#226. 翻转二叉树

翻转一棵二叉树。

示例:

输入:

1
2
3
4
5
     4
/ \
2 7
/ \ / \
1 3 6 9

输出:

1
2
3
4
5
     4
/ \
7 2
/ \ / \
9 6 3 1

备注:

这个问题是受到Max Howell原问题启发的:

谷歌:我们 90%的工程师使用您编写的软件(Homebrew),但是您却无法在面试时在白板上写出翻转二叉树这道题,这太糟糕了。

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package xyz.onns.leetcode;

/**
* @Author Onns
* @Date 2020/9/16 9:41 AM
* @Version 1.0
* @Website https://onns.xyz/blog/
*/
public class InvertBinaryTree {
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class TreeNode {
int val;
TreeNode left;
TreeNode right;

TreeNode(int x) {
val = x;
}
}

class Solution {
public TreeNode invertTree(TreeNode root) {
if (root == null) return root;
exchange(root);
return root;
}

void exchange(TreeNode root) {


TreeNode t = root.left;
root.left = root.right;
root.right = t;
if (root.left != null) {
exchange(root.left);
}
if (root.right != null) {
exchange(root.right);
}
}
}
}