LeetCode----Invert Binary Tree

/**

 * 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) {

        if(root==NULL) return root;

        TreeNode *p;

        p=root->left;

        root->left=root->right;

        root->right=p;

        invertTree(root->left);

        invertTree(root->right);

        return root;

    }

};