leetcode Invert Binary Tree

Invert a binary tree.

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

to

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

比较简单，二叉树里的题其实有点举一反三的意思，很多题会一道就差不多了。递归的反转左子树右子树就好了。

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        TreeNode* temp;
        if(root==NULL) return root;
        if(root->left==NULL&&root->right==NULL) return root;
        else{
        temp=root->left;
        root->left=invertTree(root->right);
        root->right=invertTree(temp);
        }
        
        
    }
};