Unicorns VO 面试真题解析：无重复字符的最长子串

Longest Substring Without Repeating Characters

Given a string, find the longest substring that does not contain any repeated characters.

Example 1:

Input: "abcabcbb"
Output: "abc"
Explanation: The longest substring without repeating characters is "abc".

Example 2:

Input: "bbbbb"
Output: "b"
Explanation: The longest substring without repeating characters is "b".

Example 3:

Input: "pwwkew"
Output: "wke"
Explanation: The longest substring without repeating characters is "wke".

Implement the following method:

class Solution {public String longestSubstring(String s) {}}

这道题要求在字符串中找到不含重复字符的最长子串，核心思路通常是使用滑动窗口配合哈希集合或哈希表维护窗口内字符是否重复。右指针不断扩展窗口，遇到重复字符时再移动左指针收缩窗口，从而在一次遍历中更新当前最长区间。题目示例分别展示了全不重复、全重复以及中间出现重复字符的情况，非常适合用双指针来处理，时间复杂度可做到线性级别。