leetcode 226: Invert Binary Tree，leetcodeinvert

leetcode 226: Invert Binary Tree，leetcodeinvert
Invert Binary TreeTotal Accepted: 11286 Total Submissions: 32033

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]

遞迴交換左右子樹

[CODE]

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