Add 938-RangeSumOfBST.cpp

Author: Rocky-Dewan

Leet_Code/Random Problem/938-RangeSumOfBST.cpp

@@ -0,0 +1,28 @@
+/**
+ * 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) {}
+ * };
+ */
+
+void dfs(TreeNode* root, int low, int high, int &sum){
+    if(root == nullptr){return;}
+    if(low <= root->val && root->val <= high){sum += root->val;}
+    dfs(root->left,  low, high, sum);
+    dfs(root->right, low, high, sum);
+}
+
+class Solution {
+public:
+    int rangeSumBST(TreeNode* root, int low, int high) {
+        int total(0);
+        dfs(root, low, high, total);
+        return total;
+        
+    }
+};