LeetCode in Kotlin

938. Range Sum of BST

Easy

Given the root node of a binary search tree and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [low, high].

Example 1:

Input: root = [10,5,15,3,7,null,18], low = 7, high = 15

Output: 32

Explanation: Nodes 7, 10, and 15 are in the range [7, 15]. 7 + 10 + 15 = 32.

Example 2:

Input: root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10

Output: 23

Explanation: Nodes 6, 7, and 10 are in the range [6, 10]. 6 + 7 + 10 = 23.

Constraints:

• The number of nodes in the tree is in the range [1, 2 * 104].
• 1 <= Node.val <= 105
• 1 <= low <= high <= 105
• All Node.val are unique.

Solution

import com_github_leetcode.TreeNode

/*
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {
    fun rangeSumBST(root: TreeNode?, low: Int, high: Int): Int {
        var ans = 0
        if (root == null) return 0
        if (root.`val` in low..high) {
            ans += root.`val`
        }
        if (root.`val` in low..high) {
            ans += rangeSumBST(root.left, low, high)
            ans += rangeSumBST(root.right, low, high)
        } else if (root.`val` >= low && root.`val` >= high) {
            ans += rangeSumBST(root.left, low, high)
        } else {
            ans += rangeSumBST(root.right, low, high)
        }
        return ans
    }
}

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