[leetcode][string] Longest Substring Without Repeating Characters

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题目：Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

class Solution {public:    int lengthOfLongestSubstring(string s) {if (s.size() <= 1) return s.size();int hashTable[256];memset(hashTable, -1, sizeof(hashTable));//初始化hashTableint maxLen = 0;//最长无重复字符的子串长度int len = 0;//当前无重复字符子串的长度int start = 0;//当前无重复字符子串的开始位置for (int i = 0; i < s.size(); ++i){if (hashTable[s[i]] < 0){len++;hashTable[s[i]] = i;}else{maxLen = len > maxLen ? len : maxLen;//更新最长所求子串长度for (int j = start; j < i && s[j] != s[i]; ++j){ //！！！将出现s[i]前一次出现位置之前出现的字符在hashTable全部更新为未出现过hashTable[s[j]] = -1;}len = i - hashTable[s[i]];//更新当前无重复字符子串的长度(hashTable[s[i]]是上一次字符s[i]出现的位置，所以当前无重复字符子串是从此位置到i)start = hashTable[s[i]]+1;//更新当前无重复字符子串的开始位置的下一个位置hashTable[s[i]] = i;//更新字符是s[i]出现的位置为i}}maxLen = len > maxLen ? len : maxLen;//更新最长所求子串长度（可能还没来得及更新max就到达字符串结尾了）return maxLen;}};

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