[leetcode] 938. Range Sum of BST

 

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int rangeSumBST(TreeNode* root, int low, int high) {
        if(!root) return 0;
        
        if(root->val < low) return rangeSumBST(root->right, low, high);
        else if(low <= root->val && root->val <= high) return root->val + rangeSumBST(root->left, low, high) + rangeSumBST(root->right, low, high);
        else return rangeSumBST(root->left, low, high);
        
    }
};

 

단순 Recursion으로 구현 

시간복잡도 : O(n) 

다른사람들 풀이는 Inorder Traversal 사용하던데 큰 차이는 없을듯