LeetCode OJ ---- Longest Substring Without Repeating Characters

题目描述

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.

code(c++)

/*法一：*/class Solution {public:    int lengthOfLongestSubstring(string s) {        unordered_map<char, int> subString;        int max_subLength = 0;        int start = 0;        int length;        for (int i = 0; i < s.size(); ++i){            unordered_map<char, int>::iterator it =                                 subString.find(s[i]);            if (it != subString.end()){                if (it->second >= start)                    start = it->second + 1;                         it->second = i;            }            else                subString.insert(make_pair(s[i], i));            length = i - start + 1;            max_subLength = max_subLength >             length ? max_subLength : length;        }        return max_subLength;    }};/*法二：*/class Solution {public:    int lengthOfLongestSubstring(string s) {        const size_t letterNum = 95;    //ASCII可打印字符个数        int subString[letterNum];   //记录对应元素在s中的位置        fill(subString, subString+letterNum, -1);        size_t start = 0;        size_t maxLength = 0;        size_t length;        for(size_t i = 0; i < s.size(); ++i){            if(subString[s[i] - ' '] != -1 &&             subString[s[i] - ' '] >= start)                start = subString[s[i] - ' '] + 1;            subString[s[i] - ' '] = i;            length = subString[s[i] - ' '] - start + 1;            maxLength = maxLength > length ? maxLength : length;        }        return maxLength;    }};

note:

• 对于方法二，需要知道ASCII中可打印字符的个数以及第一个可打印字符。ASCII共有128个字符，其中可打印字符有95个，控制字符有33个，可打印字符中第一个元素为空格，其ASCII值为32