Longest Substring Without Repeating Characters(算法分析week4)

Longest Substring Without Repeating Characters

题目来源：https://leetcode.com/problems/

-问题描述-
-解题思路-
-代码实现-

问题描述

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.

解题思路

(1)用数组exist保存在目前子串中出现的字符的位置；
(2)若下一个字符在子串中出现过，则子串的开始位置从已出现字符的下一位置开始，结束位置加1；
(3)若下一字符未在子串中出现过，则子串结束位置加1；
(4)子串结束位置每加1，判断子串长度如果大于max_len，则max_len等于子串长度，否则，max_len不变。

代码实现

@requires_authorizationclass Solution {public:    int lengthOfLongestSubstring(string s) {        int exist[300];        memset(exist, -1, sizeof(exist));        int begin = 0;        int end = 0;        int max_len = 0;        for (end = 0; end < s.length(); end++) {            if (exist[s[end]] >= begin) {                begin = exist[s[end]] + 1;            }            if (end - begin + 1 > max_len) {                max_len = end - begin + 1;            }            exist[s[end]] = end;        }        return max_len;    }};