二叉树前序遍历
# 构造如下二叉树
# 1
# / \
# 2 3
# / \
# 4 5
class TreeNode:def __init__(self,val=0,left = None,right = None):self.val = valself.left = leftself.right = rightdef preorderTravel(root):ans = []def preorder(node):if not node:returnans.append(node.val)preorder(node.left)preorder(node.right)preorder(root)return ansnode4 = TreeNode(4)
node5 = TreeNode(5)
node3 = TreeNode(3)
node2 = TreeNode(2,node4,node5)
root = TreeNode(1,node2,node3)
ans = preorderTravel(root)
print(ans)