226_Invert Binary Tree.cpp

/**
 * 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 root;
        
        if ( root->left == NULL && root->right == NULL )
            return root;
        
        TreeNode* l = invertTree(root->left);
        TreeNode* r = invertTree(root->right);
        
        root->left = r;
        root->right = l;
        
        return root;
    }
};