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.

链接： http://leetcode.com/problems/invert-binary-tree/ 

题解：

其实我还加这哥们LinkedIn了...后来他被Apple录取了，挺好的。 使用Recursive比较快就能写出来。

Time Complexity - O(n)， Space Complexity - O(n)。

/**
 * 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 root;
        TreeNode left = root.left;
        root.left = invertTree(root.right);
        root.right = invertTree(left);
        
        return root;
    }
}

Reference:

https://leetcode.com/discuss/40001/straightforward-dfs-recursive-iterative-bfs-solutions

226. Invert Binary Tree

原文：http://www.cnblogs.com/yrbbest/p/4994276.html