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98. 验证二叉搜索树 ​

  • 题号：98
  • 来源：LeetCode
  • 难度：中等
  • 标签：树 二叉搜索树 DFS
  • 语言：TypeScript
  • 解法：1 个
  • 作者：lmliheng
  • 最近更新：2026-09-27

TypeScript · O(n) 时间 · O(n) 空间 · 更新于 2026-09-27

中序遍历收集后判严格递增，未提前返回

typescript
/**
 * @difficulty medium
 * @tags 树,二叉搜索树,DFS
 * @time O(n)
 * @space O(n)
 * @note 中序遍历收集后判严格递增，未提前返回
 * @98. 验证二叉搜索树
 */

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)
    }
}

let root: TreeNode = new TreeNode(4, new TreeNode(2), new TreeNode(5, null, new TreeNode(6)))

// new TreeNode(5, new TreeNode(1), new TreeNode(4,new TreeNode(3),new TreeNode(6)))
console.log(root)
if (!root) { console.log(true) }

let arr: number[] = []
let res: boolean = true
const dfs = (root: TreeNode | null): void => {
    if (!root) { return }
    if (root.left) { dfs(root.left) }
    console.log(root.val)
    arr.push(root.val)
    if (root.right) { dfs(root.right) }
}
dfs(root)

for (let i = 0; i < arr.length - 1; i++) {
    if (arr[i] >= arr[i+1]) {
        // return false
    }
}
console.log(res)

export {};

源码：ts/leetcode/98. 验证二叉搜索树.ts

在 GitHub 上查看题目所在目录：lmliheng/algorithm