LeetCode@Tree_226_Invert_Binary_Tree

problem:

invert a binary tree.

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

to

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

java:

/** * 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;else{TreeNode temp = new TreeNode(root.val);temp.left = invertTree(root.right);temp.right = invertTree(root.left);return temp;}}}