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1 /**
2 * Definition for a binary tree node.
3 * public class TreeNode {
4 * int val;
5 * TreeNode left;
6 * TreeNode right;
7 * TreeNode(int x) { val = x; }
8 * }
9 */
10 class Solution {
11 public TreeNode invertTree(TreeNode root) {
12 // base case
13 if(root == null){
14 return null;
15 }
16 invertTree(root.left);
17 invertTree(root.right);
18 TreeNode tmp = root.left;
19 root.left = root.right;
20 root.right = tmp;
21 return root;
22 }
23 }
时间复杂度 O(n)
空间复杂度 O(logn)-O(n)