leetcode 226. 翻转二叉树

leetcode

/**
 * 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 ) {

            return NULL;
        }

        if ( root -> left ) {

            invertTree( root -> left );
        }

        if ( root -> right ) {

            invertTree( root -> right );
        }

        TreeNode *temp = root -> left;
        root -> left = root -> right;
        root -> right = temp;

        return root;
    }
};