LeetCode_ Invert Binary Tree

226. Invert Binary Tree

Total Accepted: 60170 Total Submissions: 140987 Difficulty: Easy

Invert a binary tree.

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

to

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

Trivia:
如题，将一个二叉树翻转：

public class Solution {    public TreeNode invertTree(TreeNode root) {        /*if(root!=null){        TreeNode temp=root.left;        temp.val=root.left.val;        root.left=root.right;        root.left.val=root.right.val;        root.right=temp;        root.right.val=temp.val;        }        return root;        */        if(root==null) return root;        TreeNode temp;        temp=root.left;        root.left=invertTree(root.right);        root.right=invertTree(temp);        return root;    }}

注释部分提交后会出现空指针错误。使用了递归的思想，有较强的借鉴意义！