【Leetcode-easy-226】Invert Binary Tree

【Leetcode-easy-226】Invert Binary Tree

题目

Invert a binary tree.

4
/   \
2     7
/ \   / \
1   3 6   9

to

4
/   \
7     2
/ \   / \
9   6 3   1

Trivia:

This problem was inspired by this original tweet by Max Howell:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

思路

递归

和剑指offer 面试题19 二叉树的镜像基本一样。

程序

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class Solution {

public TreeNode invertTree(TreeNode root) {
mirrorTree(root);
return root;
}

private void mirrorTree(TreeNode root) {
if (root == null) return;

TreeNode tmp = root.left;
root.left = root.right;
root.right = tmp;

mirrorTree(root.left);
mirrorTree(root.right);
}
}

声明：题目来自Leetcode。