leetcode第三题：求给定字符串中最长无重复子串的长度

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);