7 DEC 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 sum = 0;
    
    void inorder(TreeNode* root, int L, int R){
        if(root->left)inorder(root->left, L, R);
        if(root->val>=L && root->val<=R)sum+=root->val;
        if(root->right)inorder(root->right, L, R);
    }
    int rangeSumBST(TreeNode* root, int L, int R) {
        
        //SOLUCHAN STARTS HERE - DUN DUN DUN DUN 
        inorder(root, L, R);
        return sum;
    }
};