2021年10月1日（938. 二叉搜索树的范围和 ）

本文首发于 语雀文档

重点：

代码：

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */
function rangeSumBST(root: TreeNode | null, low: number, high: number): number {
    if (root === null) return 0
    let sum = 0
    const check = (root: TreeNode | null) => {
        if (root === null) return
        check(root.left)
        check(root.right)
        if (root.val >= low && root.val <= high) {
            sum = sum + root.val
        }
    }
    check(root.left)
    check(root.right)
    if (root.val >= low && root.val <= high) {
        sum = sum + root.val
    }
    return sum
};