leetcode第三题：求给定字符串中最长无重复子串的长度

最新推荐文章于 2022-11-18 16:18:29 发布

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最新推荐文章于 2022-11-18 16:18:29 发布

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分类专栏：数据结构与算法

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本文介绍了一种解决最长无重复字符子串问题的方法，并通过PHP实现了一个具体示例。该算法利用滑动窗口思想，有效地找到给定字符串中最长的不包含重复字符的子串。

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Given a string, find the length of the longest substring without repeating characters.

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

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<?php
/**
 * Created by PhpStorm.
 * User: polestar
 * Date: 16/11/15
 * Time: 下午6:19
 *
 */
function lengthOfLongestSubstring($string){
    $sArr = str_split($string);
    $countDict = array();
    $ans = $start = $end = 0;
    foreach($sArr as $i){
        $end += 1;
        $countDict[$i] = isset($countDict[$i])? $countDict[$i]+1 : 1;
        while ($countDict[$i] > 1) {
            $countDict[$string[$start]] -= 1;
            $start += 1;
        }
        $ans = max($ans,$end - $start);
    }
    return $ans;
}

$str = 'abctbtyuefg';
echo lengthOfLongestSubstring($str);