RangeSumOfBST.js

// Source : https://leetcode.com/problems/range-sum-of-bst/
// Author : Dean Shi
// Date   : 2019-01-10

/***************************************************************************************
 *
 * Given the root node of a binary search tree, return the sum of values of all nodes
 * with value between L and R (inclusive).
 *
 * The binary search tree is guaranteed to have unique values.
 *
 * Example 1:
 *
 * Input: root = [10,5,15,3,7,null,18], L = 7, R = 15
 * Output: 32
 *
 * Example 2:
 *
 * Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10
 * Output: 23
 *
 * Note:
 *
 * The number of nodes in the tree is at most 10000.
 * The final answer is guaranteed to be less than 2^31.
 *
 ***************************************************************************************/

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} L
 * @param {number} R
 * @return {number}
 */
var rangeSumBST = function(root, L, R) {
    let result = 0
    const stack = [root]

    while (stack.length) {
        const node = stack.pop()

        if (node) {
            if (L <= node.val && node.val <= R) {
                result += node.val
            }
            if (L < node.val) {
                stack.push(node.left)
            }
            if (node.val < R) {
                stack.push(node.right)
            }
        }
    }
    return result
};