669.trim-a-binary-search-tree.cpp

/*
 * @lc app=leetcode id=669 lang=cpp
 *
 * [669] Trim a Binary Search Tree
 */

// @lc code=start
/**
 * 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* trimBST(TreeNode* root, int L, int R) {
       if (root==NULL)
       {
           return NULL;
       }
       if (root->val<L)
       {
           return trimBST(root->right, L, R);
       }
       if (root->val>R)
       {
           return trimBST(root->left, L, R);
       }
       root->left = trimBST(root->left, L, R);
       root->right = trimBST(root->right, L, R);
       return root;
    }
};
// @lc code=end