市场营销网站,用html建设网站,营销型网站解决方案,winserver安装Wordpress以下是 LeetCode Top 100 面试必备题目及其解决方案示例。这些题目涵盖了数据结构、算法、动态规划、回溯等多种重要的面试话题。希望各位同学有所收货#xff0c;早日脱离底层到达彼岸#xff01;
1. Two Sum
题目: 给定一个整数数组 nums 和一个目标值 target#xff0c…以下是 LeetCode Top 100 面试必备题目及其解决方案示例。这些题目涵盖了数据结构、算法、动态规划、回溯等多种重要的面试话题。希望各位同学有所收货早日脱离底层到达彼岸
1. Two Sum
题目: 给定一个整数数组 nums 和一个目标值 target找出数组中两个数的和等于目标值的索引。解决方案:public int[] TwoSum(int[] nums, int target) {var map new Dictionaryint, int();for (int i 0; i nums.Length; i) {int complement target - nums[i];if (map.ContainsKey(complement)) {return new int[] { map[complement], i };}map[nums[i]] i;}throw new ArgumentException(No two sum solution);
}2. Add Two Numbers
题目: 给定两个非空链表表示两个非负整数每个节点表示一个数字返回它们的和。解决方案:public ListNode AddTwoNumbers(ListNode l1, ListNode l2) {var dummy new ListNode(0);var p l1;var q l2;var current dummy;int carry 0;while (p ! null || q ! null) {int x (p ! null) ? p.val : 0;int y (q ! null) ? q.val : 0;int sum carry x y;carry sum / 10;current.next new ListNode(sum % 10);current current.next;if (p ! null) p p.next;if (q ! null) q q.next;}if (carry 0) {current.next new ListNode(carry);}return dummy.next;
}3. Longest Substring Without Repeating Characters
题目: 给定一个字符串找出其中最长的没有重复字符的子串的长度。解决方案:public int LengthOfLongestSubstring(string s) {var map new Dictionarychar, int();int left 0;int maxLength 0;for (int right 0; right s.Length; right) {if (map.ContainsKey(s[right])) {left Math.Max(map[s[right]] 1, left);}map[s[right]] right;maxLength Math.Max(maxLength, right - left 1);}return maxLength;
}4. Median of Two Sorted Arrays
题目: 给定两个排序数组找出它们的中位数。解决方案:public double FindMedianSortedArrays(int[] nums1, int[] nums2) {int m nums1.Length, n nums2.Length;int i 0, j 0;int mid1 (m n 1) / 2;int mid2 (m n 2) / 2;int num1 0, num2 0;while (i m || j n) {if (i m (j n || nums1[i] nums2[j])) {num1 nums1[i];} else {num1 nums2[j];}if (i j mid1) {num1 num2;}if (i j mid2) {num2 num1;break;}}return (m n) % 2 0 ? (num1 num2) / 2.0 : num2;
}5. Longest Palindromic Substring
题目: 找出给定字符串中的最长回文子串。解决方案:public string LongestPalindrome(string s) {if (s.Length 0) return ;string longest ;for (int i 0; i s.Length; i) {string odd ExpandAroundCenter(s, i, i);string even ExpandAroundCenter(s, i, i 1);string longer odd.Length even.Length ? odd : even;if (longer.Length longest.Length) {longest longer;}}return longest;
}private string ExpandAroundCenter(string s, int left, int right) {while (left 0 right s.Length s[left] s[right]) {left--;right;}return s.Substring(left 1, right - left - 1);
}6. Zigzag Conversion
题目: 将一个字符串按照指定的行数进行 Zigzag 转换。解决方案:public string Convert(string s, int numRows) {if (numRows 1) return s;var rows new char[Math.Min(numRows, s.Length)][];for (int i 0; i rows.Length; i) rows[i] new char[s.Length];int curRow 0;bool goingDown false;foreach (char c in s) {rows[curRow][0] c;if (curRow 0 || curRow numRows - 1) goingDown !goingDown;curRow goingDown ? 1 : -1;}var result new StringBuilder();foreach (var row in rows) {foreach (var ch in row) {if (ch ! \0) result.Append(ch);}}return result.ToString();
}7. Reverse Integer
题目: 反转一个整数。解决方案:public int Reverse(int x) {int rev 0;while (x ! 0) {int pop x % 10;x / 10;if (rev Int32.MaxValue / 10 || (rev Int32.MaxValue / 10 pop 7)) return 0;if (rev Int32.MinValue / 10 || (rev Int32.MinValue / 10 pop -8)) return 0;rev rev * 10 pop;}return rev;
}8. String to Integer (atoi)
题目: 将字符串转换为整数。解决方案:public int MyAtoi(string s) {int i 0, sign 1, result 0;while (i s.Length s[i] ) i;if (i s.Length (s[i] || s[i] -)) {sign s[i] - ? -1 : 1;i;}while (i s.Length Char.IsDigit(s[i])) {int digit s[i] - 0;if (result Int32.MaxValue / 10 || (result Int32.MaxValue / 10 digit 7)) return sign 1 ? Int32.MaxValue : Int32.MinValue;result result * 10 digit;i;}return result * sign;
}9. Palindrome Number
题目: 判断一个整数是否是回文数。解决方案:public bool IsPalindrome(int x) {if (x 0 || (x % 10 0 x ! 0)) return false;int reversed 0, original x;while (x 0) {reversed reversed * 10 x % 10;x / 10;}return original reversed;
}10. Regular Expression Matching
题目: 实现正则表达式匹配。解决方案:
public bool IsMatch(string s, string p) {bool[,] dp new bool[s.Length 1, p.Length 1];dp[0, 0] true;for (int j 1; j p.Length; j) {if (p[j - 1] *) {dp[0, j] dp[0, j - 2];}}for (int i 1; i s.Length; i) {for (int j 1; j p.Length; j) {if (p[j - 1] s[i - 1] || p[j - 1] .) {dp[i, j] dp[i - 1, j - 1];} else if (p[j - 1] *) {dp[i, j] dp[i, j - 2] || (dp[i - 1, j] (s[i - 1] p[j - 2] || p[j - 2] .));}}}return dp[s.Length, p.Length];
}
11. Container With Most Water
题目: 找出容器中可以容纳最多水的两条线。解决方案: public int MaxArea(int[] height) {int left 0, right height.Length - 1;int maxArea 0;while (left right) {int width right - left;int minHeight Math.Min(height[left], height[right]);maxArea Math.Max(maxArea, width * minHeight);if (height[left] height[right]) {left;} else {right--;}}return maxArea;}12. Integer to Roman
题目: 将整数转换为罗马数字。解决方案:public string IntToRoman(int num) {var values new int[] { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };var symbols new string[] { M, CM, D, CD, C, XC, L, XL, X, IX, V, IV, I };var sb new StringBuilder();for (int i 0; i values.Length; i) {while (num values[i]) {sb.Append(symbols[i]);num - values[i];}}return sb.ToString();
}13. Roman to Integer
题目: 将罗马数字转换为整数。解决方案:public int RomanToInt(string s) {var map new Dictionarychar, int {{I, 1}, {V, 5}, {X, 10}, {L, 50}, {C, 100}, {D, 500}, {M, 1000}};int total 0;for (int i 0; i s.Length; i) {int value map[s[i]];if (i s.Length - 1 value map[s[i 1]]) {total - value;} else {total value;}}return total;
}14. Longest Common Prefix
题目: 找出一组字符串的最长公共前缀。解决方案:public string LongestCommonPrefix(string[] strs) {if (strs.Length 0) return ;string prefix strs[0];for (int i 1; i strs.Length; i) {while (strs[i].IndexOf(prefix) ! 0) {prefix prefix.Substring(0, prefix.Length - 1);if (prefix.Length 0) return ;}}return prefix;
}15. 3Sum
题目: 给定一个整数数组找出所有和为零的三元组。解决方案:public IListIListint ThreeSum(int[] nums) {var result new ListIListint();Array.Sort(nums);for (int i 0; i nums.Length - 2; i) {if (i 0 nums[i] nums[i - 1]) continue;int left i 1, right nums.Length - 1;while (left right) {int sum nums[i] nums[left] nums[right];if (sum 0) {left;} else if (sum 0) {right--;} else {result.Add(new Listint { nums[i], nums[left], nums[right] });while (left right nums[left] nums[left 1]) left;while (left right nums[right] nums[right - 1]) right--;left;right--;}}}return result;
}16. 4Sum
题目: 给定一个整数数组找出所有和为目标值的四元组。解决方案:public IListIListint FourSum(int[] nums, int target) {var result new ListIListint();Array.Sort(nums);for (int i 0; i nums.Length - 3; i) {if (i 0 nums[i] nums[i - 1]) continue;for (int j i 1; j nums.Length - 2; j) {if (j i 1 nums[j] nums[j - 1]) continue;int left j 1, right nums.Length - 1;while (left right) {int sum nums[i] nums[j] nums[left] nums[right];if (sum target) {left;} else if (sum target) {right--;} else {result.Add(new Listint { nums[i], nums[j], nums[left], nums[right] });while (left right nums[left] nums[left 1]) left;while (left right nums[right] nums[right - 1]) right--;left;right--;}}}}return result;
}17. Remove Nth Node From End of List
题目: 从链表中删除倒数第 N 个节点。解决方案:public ListNode RemoveNthFromEnd(ListNode head, int n) {var dummy new ListNode(0) { next head };var first dummy;var second dummy;for (int i 1; i n 1; i) {first first.next;}while (first ! null) {first first.next;second second.next;}second.next second.next.next;return dummy.next;
}18. Valid Parentheses
题目: 判断括号字符串是否有效。解决方案:public bool IsValid(string s) {var stack new Stackchar();foreach (char c in s) {if (c ( || c { || c [) {stack.Push(c);} else {if (stack.Count 0) return false;char top stack.Pop();if (c ) top ! () return false;if (c } top ! {) return false;if (c ] top ! [) return false;}}return stack.Count 0;
}19. Merge Two Sorted Lists
题目: 合并两个已排序的链表。解决方案:public ListNode MergeTwoLists(ListNode l1, ListNode l2) {var dummy new ListNode(0);var current dummy;while (l1 ! null l2 ! null) {if (l1.val l2.val) {current.next l1;l1 l1.next;} else {current.next l2;l2 l2.next;}current current.next;}if (l1 ! null) current.next l1;if (l2 ! null) current.next l2;return dummy.next;
}20. Generate Parentheses
题目: 生成所有合法的括号组合。解决方案:public IListstring GenerateParenthesis(int n) {var result new Liststring();Generate(result, , 0, 0, n);return result;
}private void Generate(IListstring result, string s, int left, int right, int n) {if (s.Length 2 * n) {result.Add(s);return;}if (left n) Generate(result, s (, left 1, right, n);if (right left) Generate(result, s ), left, right 1, n);
}21. Swap Nodes in Pairs
题目: 交换链表中相邻的节点。解决方案: public ListNode SwapPairs(ListNode head) {var dummy new ListNode(0) { next head };var current dummy;while (current.next ! null current.next.next ! null) {var first current.next;var second current.next.next;first.next second.next;second.next first;current.next second;current first;}return dummy.next;}22. Remove Duplicates from Sorted Array
题目: 从已排序数组中删除重复项。解决方案: public int RemoveDuplicates(int[] nums) {if (nums.Length 0) return 0;int j 0;for (int i 1; i nums.Length; i) {if (nums[i] ! nums[j]) {j;nums[j] nums[i];}}return j 1;}23. Search Insert Position
题目: 查找给定值在已排序数组中的插入位置。解决方案:public int SearchInsert(int[] nums, int target) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] target) return mid;if (nums[mid] target) left mid 1;else right mid - 1;}return left;
}24. Count and Say
题目: 输出第 n 项 “Count and Say” 序列。解决方案:public string CountAndSay(int n) {if (n 1) return 1;var previous CountAndSay(n - 1);var sb new StringBuilder();int count 1;for (int i 1; i previous.Length; i) {if (previous[i] previous[i - 1]) {count;} else {sb.Append(count).Append(previous[i - 1]);count 1;}}sb.Append(count).Append(previous[previous.Length - 1]);return sb.ToString();
}25. Valid Sudoku
题目: 判断给定的 9x9 数独是否有效。解决方案:public bool IsValidSudoku(char[][] board) {var rows new HashSetstring[9];var cols new HashSetstring[9];var boxes new HashSetstring[9];for (int i 0; i 9; i) {rows[i] new HashSetstring();cols[i] new HashSetstring();boxes[i] new HashSetstring();}for (int i 0; i 9; i) {for (int j 0; j 9; j) {char c board[i][j];if (c .) continue;if (!rows[i].Add(c row i) ||!cols[j].Add(c col j) ||!boxes[(i / 3) * 3 j / 3].Add(c box (i / 3) * 3 j / 3)) {return false;}}}return true;
}26. Sudoku Solver
题目: 解一个数独问题。解决方案:public void SolveSudoku(char[][] board) {Solve(board);
}private bool Solve(char[][] board) {for (int i 0; i 9; i) {for (int j 0; j 9; j) {if (board[i][j] .) {for (char c 1; c 9; c) {if (IsValid(board, i, j, c)) {board[i][j] c;if (Solve(board)) return true;board[i][j] .;}}return false;}}}return true;
}private bool IsValid(char[][] board, int row, int col, char c) {for (int i 0; i 9; i) {if (board[row][i] c || board[i][col] c ||board[3 * (row / 3) i / 3][3 * (col / 3) i % 3] c) {return false;}}return true;
}27. Word Search
题目: 给定一个二维网格和一个单词判断网格中是否存在这个单词。解决方案:public bool Exist(char[][] board, string word) {for (int i 0; i board.Length; i) {for (int j 0; j board[0].Length; j) {if (Backtrack(board, word, i, j, 0)) return true;}}return false;
}private bool Backtrack(char[][] board, string word, int i, int j, int k) {if (k word.Length) return true;if (i 0 || i board.Length || j 0 || j board[0].Length ||board[i][j] ! word[k]) return false;char temp board[i][j];board[i][j] #; // mark as visitedbool found Backtrack(board, word, i 1, j, k 1) ||Backtrack(board, word, i - 1, j, k 1) ||Backtrack(board, word, i, j 1, k 1) ||Backtrack(board, word, i, j - 1, k 1);board[i][j] temp; // unmarkreturn found;
}28. Combination Sum
题目: 给定一个数组和一个目标值找出所有可能的组合使得它们的和等于目标值。解决方案:public IListIListint CombinationSum(int[] candidates, int target) {var result new ListIListint();var combination new Listint();Backtrack(candidates, target, 0, combination, result);return result;
}private void Backtrack(int[] candidates, int target, int start, IListint combination, IListIListint result) {if (target 0) {result.Add(new Listint(combination));return;}if (target 0) return;for (int i start; i candidates.Length; i) {combination.Add(candidates[i]);Backtrack(candidates, target - candidates[i], i, combination, result);combination.RemoveAt(combination.Count - 1);}
}29. Combination Sum II
题目: 给定一个数组和一个目标值找出所有可能的组合使得它们的和等于目标值并且每个数字只能使用一次。解决方案:public IListIListint CombinationSum2(int[] candidates, int target) {var result new ListIListint();Array.Sort(candidates);var combination new Listint();Backtrack(candidates, target, 0, combination, result);return result;
}private void Backtrack(int[] candidates, int target, int start, IListint combination, IListIListint result) {if (target 0) {result.Add(new Listint(combination));return;}if (target 0) return;for (int i start; i candidates.Length; i) {if (i start candidates[i] candidates[i - 1]) continue;combination.Add(candidates[i]);Backtrack(candidates, target - candidates[i], i 1, combination, result);combination.RemoveAt(combination.Count - 1);}
}30. Permutations
题目: 给定一个不含重复数字的数组返回它们的所有排列。解决方案: public IListIListint Permute(int[] nums) {var result new ListIListint();var permutation new Listint();var used new bool[nums.Length];Backtrack(nums, used, permutation, result);return result;}private void Backtrack(int[] nums, bool[] used, IListint permutation, IListIListint result) {if (permutation.Count nums.Length) {result.Add(new Listint(permutation));return;}for (int i 0; i nums.Length; i) {if (used[i]) continue;used[i] true;permutation.Add(nums[i]);Backtrack(nums, used, permutation, result);permutation.RemoveAt(permutation.Count - 1);used[i] false;}}31. Permutations II
题目: 给定一个可能包含重复数字的数组返回它们的所有唯一排列。解决方案: public IListIListint PermuteUnique(int[] nums) {var result new ListIListint();var permutation new Listint();Array.Sort(nums);var used new bool[nums.Length];Backtrack(nums, used, permutation, result);return result;}private void Backtrack(int[] nums, bool[] used, IListint permutation, IListIListint result) {if (permutation.Count nums.Length) {result.Add(new Listint(permutation));return;}for (int i 0; i nums.Length; i) {if (used[i] || (i 0 nums[i] nums[i - 1] !used[i - 1])) continue;used[i] true;permutation.Add(nums[i]);Backtrack(nums, used, permutation, result);permutation.RemoveAt(permutation.Count - 1);used[i] false;}}32. Generate Parentheses
题目: 生成所有合法的括号组合。解决方案:public IListstring GenerateParenthesis(int n) {var result new Liststring();Generate(result, , 0, 0, n);return result;
}private void Generate(IListstring result, string s, int left, int right, int n) {if (s.Length 2 * n) {result.Add(s);return;}if (left n) Generate(result, s (, left 1, right, n);if (right left) Generate(result, s ), left, right 1, n);
}33. Spiral Matrix
题目: 给定一个 m x n 的矩阵返回它的螺旋顺序。解决方案:public IListint SpiralOrder(int[][] matrix) {var result new Listint();if (matrix.Length 0) return result;int top 0, bottom matrix.Length - 1;int left 0, right matrix[0].Length - 1;while (top bottom left right) {for (int i left; i right; i) result.Add(matrix[top][i]);top;for (int i top; i bottom; i) result.Add(matrix[i][right]);right--;if (top bottom) {for (int i right; i left; i--) result.Add(matrix[bottom][i]);bottom--;}if (left right) {for (int i bottom; i top; i--) result.Add(matrix[i][left]);left;}}return result;
}34. Rotate Image
题目: 旋转一个 n x n 的矩阵 90 度。解决方案:public void Rotate(int[][] matrix) {int n matrix.Length;// Transpose the matrixfor (int i 0; i n; i) {for (int j i; j n; j) {int temp matrix[i][j];matrix[i][j] matrix[j][i];matrix[j][i] temp;}}// Reverse each rowfor (int i 0; i n; i) {for (int j 0; j n / 2; j) {int temp matrix[i][j];matrix[i][j] matrix[i][n - 1 - j];matrix[i][n - 1 - j] temp;}}
}35. Set Matrix Zeroes
题目: 如果矩阵中的某个元素为零则将该元素所在行和列的所有元素都置零。解决方案:public void SetZeroes(int[][] matrix) {bool firstRowZero false, firstColZero false;int m matrix.Length, n matrix[0].Length;for (int i 0; i m; i) {if (matrix[i][0] 0) firstColZero true;}for (int j 0; j n; j) {if (matrix[0][j] 0) firstRowZero true;}for (int i 1; i m; i) {for (int j 1; j n; j) {if (matrix[i][j] 0) {matrix[i][0] 0;matrix[0][j] 0;}}}for (int i 1; i m; i) {for (int j 1; j n; j) {if (matrix[i][0] 0 || matrix[0][j] 0) {matrix[i][j] 0;}}}if (firstRowZero) {for (int j 0; j n; j) matrix[0][j] 0;}if (firstColZero) {for (int i 0; i m; i) matrix[i][0] 0;}
}36. Sort Colors
题目: 对包含红色、白色和蓝色的数组进行排序使得所有红色排在前面白色排在中间蓝色排在最后面。解决方案:public void SortColors(int[] nums) {int red 0, white 0, blue nums.Length - 1;while (white blue) {if (nums[white] 0) {Swap(nums, red, white);} else if (nums[white] 1) {white;} else {Swap(nums, white, blue--);}}
}private void Swap(int[] nums, int i, int j) {int temp nums[i];nums[i] nums[j];nums[j] temp;
}37. Search in Rotated Sorted Array
题目: 在旋转排序数组中查找目标值。解决方案:public int Search(int[] nums, int target) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] target) return mid;if (nums[left] nums[mid]) {if (nums[left] target target nums[mid]) {right mid - 1;} else {left mid 1;}} else {if (nums[mid] target target nums[right]) {left mid 1;} else {right mid - 1;}}}return -1;
}38. Search Insert Position
题目: 查找给定值在已排序数组中的插入位置。解决方案:public int SearchInsert(int[] nums, int target) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] target) return mid;if (nums[mid] target) left mid 1;else right mid - 1;}return left;
}39. Two Sum II - Input Array Is Sorted
题目: 给定一个已排序的数组和一个目标值找出两个数之和为目标值的索引。解决方案: public int[] TwoSum(int[] numbers, int target) {int left 0, right numbers.Length - 1;while (left right) {int sum numbers[left] numbers[right];if (sum target) return new int[] { left 1, right 1 };if (sum target) left;else right--;}return new int[] { -1, -1};
}40. Majority Element
题目: 找出数组中出现次数超过 n/2 次的元素。解决方案:public int MajorityElement(int[] nums) {int count 0, candidate 0;foreach (int num in nums) {if (count 0) candidate num;count (num candidate) ? 1 : -1;}return candidate;
}好的我们继续。
41. Combination Sum III
题目: 找出所有的 k 个数使它们的和等于 n。解决方案:public IListIListint CombinationSum3(int k, int n) {var result new ListIListint();var combination new Listint();Backtrack(k, n, 1, combination, result);return result;
}private void Backtrack(int k, int n, int start, IListint combination, IListIListint result) {if (combination.Count k n 0) {result.Add(new Listint(combination));return;}for (int i start; i 9; i) {combination.Add(i);Backtrack(k, n - i, i 1, combination, result);combination.RemoveAt(combination.Count - 1);}
}42. Subsets
题目: 给定一个不含重复数字的数组返回所有可能的子集。解决方案:public IListIListint Subsets(int[] nums) {var result new ListIListint();var subset new Listint();Backtrack(nums, 0, subset, result);return result;
}private void Backtrack(int[] nums, int start, IListint subset, IListIListint result) {result.Add(new Listint(subset));for (int i start; i nums.Length; i) {subset.Add(nums[i]);Backtrack(nums, i 1, subset, result);subset.RemoveAt(subset.Count - 1);}
}43. Subsets II
题目: 给定一个可能包含重复数字的数组返回所有可能的子集。解决方案:public IListIListint SubsetsWithDup(int[] nums) {var result new ListIListint();var subset new Listint();Array.Sort(nums);Backtrack(nums, 0, subset, result);return result;
}private void Backtrack(int[] nums, int start, IListint subset, IListIListint result) {result.Add(new Listint(subset));for (int i start; i nums.Length; i) {if (i start nums[i] nums[i - 1]) continue;subset.Add(nums[i]);Backtrack(nums, i 1, subset, result);subset.RemoveAt(subset.Count - 1);}
}44. Reverse Bits
题目: 反转给定的 32 位无符号整数的二进制位。解决方案:public uint ReverseBits(uint n) {uint result 0;for (int i 0; i 32; i) {result (result 1) | (n 1);n 1;}return result;
}45. Hamming Distance
题目: 计算两个整数之间的汉明距离。解决方案:public int HammingDistance(int x, int y) {return CountBits(x ^ y);
}private int CountBits(int n) {int count 0;while (n 0) {count n 1;n 1;}return count;
}46. Single Number
题目: 给定一个非空整数数组其中每个元素都出现两次除了一个元素只出现了一次找出那个只出现一次的元素。解决方案:public int SingleNumber(int[] nums) {int result 0;foreach (int num in nums) {result ^ num;}return result;
}47. Missing Number
题目: 给定一个包含 0 到 n 的所有整数的数组除了其中一个整数缺失找出缺失的那个整数。解决方案:public int MissingNumber(int[] nums) {int n nums.Length;int total n * (n 1) / 2;int sum 0;foreach (int num in nums) {sum num;}return total - sum;
}48. Find the Duplicate Number
题目: 给定一个包含 n 1 个整数的数组其中每个整数都在 1 到 n 之间找出重复的那个数字。解决方案:public int FindDuplicate(int[] nums) {int slow nums[0];int fast nums[0];do {slow nums[slow];fast nums[nums[fast]];} while (slow ! fast);fast nums[0];while (slow ! fast) {slow nums[slow];fast nums[fast];}return slow;
}49. Linked List Cycle
题目: 判断一个链表是否有环。解决方案:public bool HasCycle(ListNode head) {var slow head;var fast head;while (fast ! null fast.next ! null) {slow slow.next;fast fast.next.next;if (slow fast) return true;}return false;
}50. Merge Intervals
题目: 合并重叠的区间。解决方案:public int[][] Merge(int[][] intervals) {if (intervals.Length 0) return new int[0][];Array.Sort(intervals, (a, b) a[0].CompareTo(b[0]));var result new Listint[]();var current intervals[0];result.Add(current);for (int i 1; i intervals.Length; i) {if (intervals[i][0] current[1]) {current[1] Math.Max(current[1], intervals[i][1]);} else {current intervals[i];result.Add(current);}}return result.ToArray();
}51. Insert Interval
题目: 在一个已排序的区间列表中插入一个新的区间并合并所有重叠的区间。解决方案:public int[][] Insert(int[][] intervals, int[] newInterval) {var result new Listint[]();int i 0, n intervals.Length;// Add all intervals ending before newInterval startswhile (i n intervals[i][1] newInterval[0]) {result.Add(intervals[i]);}// Merge all overlapping intervals to one considering newIntervalwhile (i n intervals[i][0] newInterval[1]) {newInterval[0] Math.Min(newInterval[0], intervals[i][0]);newInterval[1] Math.Max(newInterval[1], intervals[i][1]);i;}result.Add(newInterval);// Add all the restwhile (i n) {result.Add(intervals[i]);}return result.ToArray();
}52. Intervals Intersection
题目: 找出两个区间列表的交集。解决方案:public int[][] IntervalIntersection(int[][] A, int[][] B) {var result new Listint[]();int i 0, j 0;while (i A.Length j B.Length) {int start Math.Max(A[i][0], B[j][0]);int end Math.Min(A[i][1], B[j][1]);if (start end) {result.Add(new[] { start, end });}if (A[i][1] B[j][1]) {i;} else {j;}}return result.ToArray();
}53. Course Schedule
题目: 判断是否可以完成所有课程课程之间的先修关系由一个二维数组表示。解决方案:
public bool CanFinish(int numCourses, int[][] prerequisites) {var graph new Listint[numCourses];var inDegree new int[numCourses];for (int i 0; i numCourses; i) {graph[i] new Listint();}foreach (var pre in prerequisites) {graph[pre[1]].Add(pre[0]);inDegree[pre[0]];}var queue new Queueint();for (int i 0; i numCourses; i) {if (inDegree[i] 0) queue.Enqueue(i);}int count 0;while (queue.Count 0) {var node queue.Dequeue();count;foreach (var neighbor in graph[node]) {inDegree[neighbor]--;if (inDegree[neighbor] 0) queue.Enqueue(neighbor);}}return count numCourses;
}
54. Top K Frequent Elements
题目: 给定一个非空的整数数组返回出现频率前 k 高的元素。解决方案: public IListint TopKFrequent(int[] nums, int k) {var frequency new Dictionaryint, int();foreach (var num in nums) {if (frequency.ContainsKey(num)) {frequency[num];} else {frequency[num] 1;}}var sorted frequency.OrderByDescending(pair pair.Value).Take(k).Select(pair pair.Key).ToList();return sorted;}55. Kth Largest Element in an Array
题目: 找出数组中第 k 个最大的元素。解决方案:public int FindKthLargest(int[] nums, int k) {Array.Sort(nums);return nums[nums.Length - k];
}56. Valid Parentheses
题目: 判断字符串中的括号是否有效。解决方案:public bool IsValid(string s) {var stack new Stackchar();var map new Dictionarychar, char {{ ), ( },{ ], [ },{ }, { }};foreach (var ch in s) {if (map.ContainsKey(ch)) {if (stack.Count 0 || stack.Pop() ! map[ch]) return false;} else {stack.Push(ch);}}return stack.Count 0;
}57. Generate Parentheses
题目: 生成所有合法的括号组合。解决方案:public IListstring GenerateParenthesis(int n) {var result new Liststring();Generate(result, , 0, 0, n);return result;
}private void Generate(IListstring result, string s, int left, int right, int n) {if (s.Length 2 * n) {result.Add(s);return;}if (left n) Generate(result, s (, left 1, right, n);if (right left) Generate(result, s ), left, right 1, n);
}58. String to Integer (atoi)
题目: 实现 atoi 函数将字符串转换为整数。解决方案:public int MyAtoi(string s) {if (string.IsNullOrWhiteSpace(s)) return 0;int index 0, sign 1, result 0;while (index s.Length s[index] ) index;if (index s.Length (s[index] || s[index] -)) {sign s[index] ? 1 : -1;index;}while (index s.Length char.IsDigit(s[index])) {int digit s[index] - 0;if (result (int.MaxValue - digit) / 10) {return sign 1 ? int.MaxValue : int.MinValue;}result result * 10 digit;index;}return result * sign;
}59. Longest Substring Without Repeating Characters
题目: 找出一个字符串中最长的不包含重复字符的子串的长度。解决方案:public int LengthOfLongestSubstring(string s) {var map new Dictionarychar, int();int left 0, maxLength 0;for (int right 0; right s.Length; right) {if (map.ContainsKey(s[right])) {left Math.Max(map[s[right]] 1, left);}map[s[right]] right;maxLength Math.Max(maxLength, right - left 1);}return maxLength;
}60. Median of Two Sorted Arrays
题目: 查找两个排序数组的中位数。解决方案:public double FindMedianSortedArrays(int[] nums1, int[] nums2) {int m nums1.Length, n nums2.Length;if (m n) {return FindMedianSortedArrays(nums2, nums1);}int imin 0, imax m, halfLen (m n 1) / 2;while (imin imax) {int i (imin imax) / 2;int j halfLen - i;if (i m nums2[j - 1] nums1[i]) {imin i 1;} else if (i 0 nums1[i - 1] nums2[j]) {imax i - 1;} else {int maxLeft 0;if (i 0) maxLeft nums2[j - 1];else if (j 0) maxLeft nums1[i - 1];else maxLeft Math.Max(nums1[i - 1], nums2[j - 1]);if ((m n) % 2 1) return maxLeft;int minRight 0;if (i m) minRight nums2[j];else if (j n) minRight nums1[i];else minRight Math.Min(nums1[i], nums2[j]);return (maxLeft minRight) / 2.0;}}throw new ArgumentException(Input arrays are not sorted.);
}61. Search a 2D Matrix
题目: 在一个 m x n 矩阵中查找目标值。解决方案:public bool SearchMatrix(int[][] matrix, int target) {if (matrix.Length 0 || matrix[0].Length 0) return false;int m matrix.Length, n matrix[0].Length;int row 0, col n - 1;while (row m col 0) {if (matrix[row][col] target) return true;if (matrix[row][col] target) col--;else row;}return false;
}62. Word Ladder
题目: 变换一个单词到另一个单词每次只改变一个字母找出最短的变换序列长度。解决方案:public int LadderLength(string beginWord, string endWord, IListstring wordList) {var wordSet new HashSetstring(wordList);if (!wordSet.Contains(endWord)) return 0;var queue new Queuestring();queue.Enqueue(beginWord);int length 1;while (queue.Count 0) {int levelSize queue.Count;for (int i 0; i levelSize; i) {var word queue.Dequeue();if (word endWord) return length;var chars word.ToCharArray();for (int j 0; j chars.Length; j) {char originalChar chars[j];for (char c a; c z; c) {if (c originalChar) continue;chars[j] c;var newWord new string(chars);if (wordSet.Contains(newWord)) {queue.Enqueue(newWord);wordSet.Remove(newWord);}}chars[j] originalChar;}}length;}return 0;
}63. Number of Islands
题目: 给定一个 2D 网格其中 1 代表陆地0 代表水计算岛屿的数量。解决方案:
public int NumIslands(char[][] grid) {if (grid.Length 0) return 0;int m grid.Length, n grid[0].Length;int count 0;for (int i 0; i m; i) {for (int j 0; j n; j) {if (grid[i][j] 1) {DFS(grid, i, j);count;}}}return count;
}private void DFS(char[][] grid, int i, int j) {if (i 0 || i grid.Length || j 0 || j grid[0].Length || grid[i][j] 0) return;grid[i][j] 0;DFS(grid, i 1, j);DFS(grid, i - 1, j);DFS(grid, i, j 1);DFS(grid, i, j - 1);
}
64. Clone Graph
题目: 克隆一个无向图。解决方案:public Node CloneGraph(Node node) {if (node null) return null;var map new DictionaryNode, Node();var queue new QueueNode();queue.Enqueue(node);map[node] new Node(node.val);while (queue.Count 0) {var curr queue.Dequeue();foreach (var neighbor in curr.neighbors) {if (!map.ContainsKey(neighbor)) {map[neighbor] new Node(neighbor.val);queue.Enqueue(neighbor);}map[curr].neighbors.Add(map[neighbor]);}}return map[node];
}65. Serialize and Deserialize Binary Tree
题目: 实现二叉树的序列化和反序列化。解决方案:public class Codec {public string Serialize(TreeNode root) {var sb new StringBuilder();Serialize(root, sb);return sb.ToString();}private void Serialize(TreeNode root, StringBuilder sb) {if (root null) {sb.Append(null,);return;}sb.Append(root.val ,);Serialize(root.left, sb);Serialize(root.right, sb);}public TreeNode Deserialize(string data) {var nodes data.Split(,);var queue new Queuestring(nodes);return Deserialize(queue);}private TreeNode Deserialize(Queuestring queue) {var val queue.Dequeue();if (val null) return null;var node new TreeNode(int.Parse(val));node.left Deserialize(queue);node.right Deserialize(queue);return node;}
}66. Add Two Numbers
题目: 给定两个非空链表表示两个非负整数按位相加它们的值并返回一个新的链表。解决方案:public ListNode AddTwoNumbers(ListNode l1, ListNode l2) {var dummy new ListNode(0);var p dummy;var carry 0;while (l1 ! null || l2 ! null || carry ! 0) {var x (l1 ! null) ? l1.val : 0;var y (l2 ! null) ? l2.val : 0;var sum carry x y;carry sum / 10;p.next new ListNode(sum % 10);p p.next;if (l1 ! null) l1 l1.next;if (l2 ! null) l2 l2.next;}return dummy.next;
}67. Add Two Numbers II
题目: 给定两个链表表示两个非负整数按位相加它们的值并返回一个新的链表链表的数值是反向的。解决方案:public ListNode AddTwoNumbers(ListNode l1, ListNode l2) {var stack1 new Stackint();var stack2 new Stackint();while (l1 ! null) {stack1.Push(l1.val);l1 l1.next;}while (l2 ! null) {stack2.Push(l2.val);l2 l2.next;}var dummy new ListNode(0);var carry 0;while (stack1.Count 0 || stack2.Count 0 || carry 0) {var x (stack1.Count 0) ? stack1.Pop() : 0;var y (stack2.Count 0) ? stack2.Pop() : 0;var sum x y carry;carry sum / 10;var node new ListNode(sum % 10);node.next dummy.next;dummy.next node;}return dummy.next;
}68. Palindrome Linked List
题目: 判断链表是否为回文。解决方案:public bool IsPalindrome(ListNode head) {if (head null) return true;var slow head;var fast head;var stack new Stackint();while (fast ! null fast.next ! null) {stack.Push(slow.val);slow slow.next;fast fast.next.next;}if (fast ! null) slow slow.next;while (slow ! null) {if (stack.Pop() ! slow.val) return false;slow slow.next;}return true;
}69. Reverse Linked List
题目: 反转一个单链表。解决方案:public ListNode ReverseList(ListNode head) {ListNode prev null;ListNode curr head;while (curr ! null) {var next curr.next;curr.next prev;prev curr;curr next;}return prev;
}70. Merge Two Sorted Lists
题目: 合并两个排序的链表并返回合并后的链表。解决方案:public ListNode MergeTwoLists(ListNode l1, ListNode l2) {var dummy new ListNode(0);var p dummy;while (l1 ! null l2 ! null) {if (l1.val l2.val) {p.next l1;l1 l1.next;} else {p.next l2;l2 l2.next;}p p.next;}p.next (l1 ! null) ? l1 : l2;return dummy.next;
}71. Convert Sorted List to Binary Search Tree
题目: 将一个排序的链表转换为平衡的二叉搜索树。解决方案:public TreeNode SortedListToBST(ListNode head) {if (head null) return null;return ConvertToBST(ref head, 0, GetLength(head));
}private TreeNode ConvertToBST(ref ListNode head, int start, int end) {if (start end) return null;int mid (start end) / 2;TreeNode left ConvertToBST(ref head, start, mid - 1);TreeNode root new TreeNode(head.val);root.left left;head head.next;root.right ConvertToBST(ref head, mid 1, end);return root;
}private int GetLength(ListNode head) {int length 0;while (head ! null) {length;head head.next;}return length;
}72. Delete Node in a Linked List
题目: 删除链表中给定的节点。解决方案:public void DeleteNode(ListNode node) {if (node null || node.next null) return;node.val node.next.val;node.next node.next.next;
}73. Find Minimum in Rotated Sorted Array
题目: 找出旋转排序数组中的最小值。解决方案:public int FindMin(int[] nums) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] nums[right]) {left mid 1;} else {right mid;}}return nums[left];
}74. Find Peak Element
题目: 找到数组中的峰值元素。解决方案:public int FindPeakElement(int[] nums) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] nums[mid 1]) {right mid;} else {left mid 1;}}return left;
}75. Product of Array Except Self
题目: 给定一个整数数组 nums返回一个数组 outputoutput[i] 是 nums 中除了 nums[i] 外的所有元素的乘积。解决方案:public int[] ProductExceptSelf(int[] nums) {int n nums.Length;var output new int[n];var left new int[n];var right new int[n];left[0] 1;for (int i 1; i n; i) {left[i] left[i - 1] * nums[i - 1];}right[n - 1] 1;for (int i n - 2; i 0; i--) {right[i] right[i 1] * nums[i 1];}for (int i 0; i n; i) {output[i] left[i] * right[i];}return output;
}76. 3Sum
题目: 给定一个整数数组找出所有和为零的三元组。解决方案:public IListIListint ThreeSum(int[] nums) {var result new ListIListint();Array.Sort(nums);for (int i 0; i nums.Length - 2; i) {if (i 0 nums[i] nums[i - 1]) continue;int left i 1, right nums.Length - 1;while (left right) {int sum nums[i] nums[left] nums[right];if (sum 0) left;else if (sum 0) right--;else {result.Add(new Listint { nums[i], nums[left], nums[right] });while (left right nums[left] nums[left 1]) left;while (left right nums[right] nums[right - 1]) right--;left;right--;}}}return result;
}77. Group Anagrams
题目: 将一组字符串按字母异位词分组。解决方案:public IListIListstring GroupAnagrams(string[] strs) {var map new Dictionarystring, IListstring();foreach (var str in strs) {var chars str.ToCharArray();Array.Sort(chars);var key new string(chars);if (!map.ContainsKey(key)) {map[key] new Liststring();}map[key].Add(str);}return new ListIListstring(map.Values);
}78. Letter Combinations of a Phone Number
题目: 给定一个数字字符串返回所有可能的字母组合。解决方案:public IListstring LetterCombinations(string digits) {var result new Liststring();if (string.IsNullOrEmpty(digits)) return result;var phoneMap new Dictionarychar, string {{ 2, abc }, { 3, def }, { 4, ghi },{ 5, jkl }, { 6, mno }, { 7, pqrs },{ 8, tuv }, { 9, wxyz }};GenerateCombinations(phoneMap, digits, 0, new StringBuilder(), result);return result;
}private void GenerateCombinations(Dictionarychar, string phoneMap, string digits, int index, StringBuilder combination, IListstring result) {if (index digits.Length) {result.Add(combination.ToString());return;}var digit digits[index];var letters phoneMap[digit];for (int i 0; i letters.Length; i) {combination.Append(letters[i]);GenerateCombinations(phoneMap, digits, index 1, combination, result);combination.Length--;}
}79. Remove Duplicates from Sorted Array
题目: 从排序数组中移除重复项使每个元素只出现一次并返回新的长度。解决方案:public int RemoveDuplicates(int[] nums) {if (nums.Length 0) return 0;int index 1;for (int i 1; i nums.Length; i) {if (nums[i] ! nums[i - 1]) {nums[index] nums[i];}}return index;
}80. Move Zeroes
题目: 移动数组中的零使所有非零元素都在前面并保持相对顺序。解决方案:public void MoveZeroes(int[] nums) {int lastNonZeroFoundAt 0;for (int i 0; i nums.Length; i) {if (nums[i] ! 0) {Swap(nums, i, lastNonZeroFoundAt);lastNonZeroFoundAt;}}
}private void Swap(int[] nums, int i, int j) {int temp nums[i];nums[i] nums[j];nums[j] temp;
}81. Longest Common Prefix
题目: 找到字符串数组的最长公共前缀。解决方案:public string LongestCommonPrefix(string[] strs) {if (strs.Length 0) return ;var prefix strs[0];for (int i 1; i strs.Length; i) {while (strs[i].IndexOf(prefix) ! 0) {prefix prefix.Substring(0, prefix.Length - 1);if (prefix ) return ;}}return prefix;
}82. Reverse Integer
题目: 反转一个 32 位的整数。解决方案:public int Reverse(int x) {long result 0;while (x ! 0) {result result * 10 x % 10;x / 10;}if (result int.MaxValue || result int.MinValue) return 0;return (int)result;
}83. String Compression
题目: 压缩字符串只保留字符和它们的出现次数。解决方案:public int Compress(char[] chars) {int write 0, read 0;while (read chars.Length) {char currentChar chars[read];int count 0;while (read chars.Length chars[read] currentChar) {read;count;}chars[write] currentChar;if (count 1) {foreach (var digit in count.ToString()) {chars[write] digit;}}}return write;
}84. Find Minimum in Rotated Sorted Array II
题目: 在可能包含重复元素的旋转排序数组中找到最小值。解决方案:public int FindMin(int[] nums) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] nums[right]) {right mid;} else if (nums[mid] nums[right]) {left mid 1;} else {right--;}}return nums[left];
}85. Search Insert Position
题目: 给定一个排序数组和一个目标值返回目标值应该插入的位置。解决方案:public int SearchInsert(int[] nums, int target) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] target) return mid;if (nums[mid] target) left mid 1;else right mid - 1;}return left;
}86. Two Sum
题目: 给定一个整数数组和一个目标值找出数组中和为目标值的两个数字。解决方案: public int[] TwoSum(int[] nums, int target) {var map new Dictionaryint, int();for (int i 0; i nums.Length; i) {int complement target -nums[i];if (map.ContainsKey(complement)) {return new[] { map[complement], i };}map[nums[i]] i;}return null;}87. Longest Substring Without Repeating Characters
题目: 给定一个字符串找出最长的无重复字符子串。解决方案: public int LengthOfLongestSubstring(string s) {var map new Dictionarychar, int();int left 0, maxLength 0;for (int right 0; right s.Length; right) {if (map.ContainsKey(s[right])) {left Math.Max(map[s[right]] 1, left);}map[s[right]] right;maxLength Math.Max(maxLength, right - left 1);}return maxLength;}88. Longest Palindromic Substring
题目: 给定一个字符串找到最长的回文子串。解决方案:public string LongestPalindrome(string s) {if (s.Length 0) return ;string longest ;for (int i 0; i s.Length; i) {string odd ExpandAroundCenter(s, i, i);string even ExpandAroundCenter(s, i, i 1);string currentLongest odd.Length even.Length ? odd : even;if (currentLongest.Length longest.Length) {longest currentLongest;}}return longest;
}private string ExpandAroundCenter(string s, int left, int right) {while (left 0 right s.Length s[left] s[right]) {left--;right;}return s.Substring(left 1, right - left - 1);
}89. Remove Duplicates from Sorted Array II
题目: 从排序数组中删除重复项使每个元素最多出现两次。解决方案:public int RemoveDuplicates(int[] nums) {int index 0, count 0;for (int i 0; i nums.Length; i) {if (i 2 || nums[i] ! nums[index - 2]) {nums[index] nums[i];}}return index;
}90. Valid Parentheses
题目: 给定一个字符串判断括号是否有效。解决方案:public bool IsValid(string s) {var stack new Stackchar();foreach (var c in s) {if (c ( || c [ || c {) {stack.Push(c);} else {if (stack.Count 0) return false;char top stack.Pop();if ((c ) top ! () ||(c ] top ! [) ||(c } top ! {)) {return false;}}}return stack.Count 0;
}91. Generate Parentheses
题目: 生成所有有效的括号组合。解决方案:public IListstring GenerateParenthesis(int n) {var result new Liststring();Generate(result, , 0, 0, n);return result;
}private void Generate(IListstring result, string current, int open, int close, int max) {if (current.Length max * 2) {result.Add(current);return;}if (open max) {Generate(result, current (, open 1, close, max);}if (close open) {Generate(result, current ), open, close 1, max);}
}92. Unique Paths
题目: 计算从左上角到右下角的所有不同路径数。解决方案:public int UniquePaths(int m, int n) {var dp new int[m, n];for (int i 0; i m; i) {dp[i, 0] 1;}for (int j 0; j n; j) {dp[0, j] 1;}for (int i 1; i m; i) {for (int j 1; j n; j) {dp[i, j] dp[i - 1, j] dp[i, j - 1];}}return dp[m - 1, n - 1];
}93. Maximum Subarray
题目: 找到一个数组的最大子数组和。解决方案:public int MaxSubArray(int[] nums) {int maxSoFar nums[0];int maxEndingHere nums[0];for (int i 1; i nums.Length; i) {maxEndingHere Math.Max(nums[i], maxEndingHere nums[i]);maxSoFar Math.Max(maxSoFar, maxEndingHere);}return maxSoFar;
}94. Climbing Stairs
题目: 给定楼梯的阶数计算到达顶部的方法数。解决方案:public int ClimbStairs(int n) {if (n 1) return 1;int[] dp new int[n 1];dp[1] 1;dp[2] 2;for (int i 3; i n; i) {dp[i] dp[i - 1] dp[i - 2];}return dp[n];
}95. Maximum Product Subarray
题目: 找到一个数组的最大乘积子数组。解决方案:public int MaxProduct(int[] nums) {int maxSoFar nums[0];int minEndingHere nums[0];int maxEndingHere nums[0];for (int i 1; i nums.Length; i) {int tempMax maxEndingHere;maxEndingHere Math.Max(nums[i], Math.Max(maxEndingHere * nums[i], minEndingHere * nums[i]));minEndingHere Math.Min(nums[i], Math.Min(tempMax * nums[i], minEndingHere * nums[i]));maxSoFar Math.Max(maxSoFar, maxEndingHere);}return maxSoFar;
}96. Word Break
题目: 判断一个字符串是否可以被分割成字典中的单词。解决方案:public bool WordBreak(string s, IListstring wordDict) {var wordSet new HashSetstring(wordDict);var dp new bool[s.Length 1];dp[0] true;for (int i 1; i s.Length; i) {for (int j 0; j i; j) {if (dp[j] wordSet.Contains(s.Substring(j, i - j))) {dp[i] true;break;}}}return dp[s.Length];
}97. Edit Distance
题目: 计算将一个字符串转换成另一个字符串所需的最少操作数。解决方案:public int MinDistance(string word1, string word2) {int m word1.Length;int n word2.Length;var dp new int[m 1, n 1];for (int i 0; i m; i) dp[i, 0] i;for (int j 0; j n; j) dp[0, j] j;for (int i 1; i m; i) {for (int j 1; j n; j) {if (word1[i - 1] word2[j - 1]) {dp[i, j] dp[i - 1, j - 1];} else {dp[i, j] 1 Math.Min(dp[i - 1, j], Math.Min(dp[i, j - 1], dp[i - 1, j - 1]));}}}return dp[m, n];
}98. Search in Rotated Sorted Array
题目: 在旋转排序数组中查找目标值。解决方案: public int Search(int[] nums, int target) {int left 0, right nums.Length - 1;while (left right) {int mid left (right - left) / 2;if (nums[mid] target) return mid;if (nums[left] nums[mid]) {if (nums[left] target target nums[mid]) {right mid - 1;} else {left mid 1;}} else {if (nums[mid] target target nums[right]) {left mid 1;} else {right mid - 1;}}}return -1;}99. Best Time to Buy and Sell Stock
题目: 给定一个数组找出最大利润。解决方案:public int MaxProfit(int[] prices) {int minPrice int.MaxValue;int maxProfit 0;foreach (var price in prices) {minPrice Math.Min(minPrice, price);maxProfit Math.Max(maxProfit, price - minPrice);}return maxProfit;
}100. Longest Substring with At Most Two Distinct Characters
题目: 找到包含至多两个不同字符的最长子串。解决方案:public int LengthOfLongestSubstringTwoDistinct(string s) {var map new Dictionarychar, int();int left 0, maxLength 0;for (int right 0; right s.Length; right) {map[s[right]] right;if (map.Count 2) {var minIndex int.MaxValue;foreach (var index in map.Values) {minIndex Math.Min(minIndex, index);}map.Remove(s[minIndex]);left minIndex 1;}maxLength Math.Max(maxLength, right - left 1);}return maxLength;
}
