LeetCode-Invert Binary Tree

• problem：

Invert a binary tree.

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

to

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

• analysis：

利用递归将root的左节点赋值为转换了右子树的右节点，将root的右节点赋值为转换了左子树的左节点，并返回root。

• anwser：

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