Leetcode 226 flip binary tree (recursive)

226. Flip binary tree

The difficulty is simple 573

Turn over a binary tree .

Example ：

Input ：

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

Output ：

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

  Ideas ： Just flip recursively , Flip the root first , Then flip the left subtree , Then flip the right subtree .

 

/**
 * 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 NULL;}
        TreeNode* temp = root->left;
        root->left = root->right;
        root->right = temp;
        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};