12.5—贪心法—Longest Substring Without Repeating Characters

描述
Given a string, find the length of the longest substring without repeating characters. For example, the
longest substring without repeating leers for ”abcabcbb” is ”abc”, which the length is 3. For ”bbbbb”

the longest substring is ”b”, with the length of 1.注：（LeetCode上面解法的复杂度不是它所说的O(n)）

#include<iostream>#include<vector>#include<string>using namespace std;//找最长的没有重复字符的子串pair<int, string> FindLongestSubstrNoRep(const string &str){if (str == "")return make_pair(0, "");//===vector<int> hashtable(256, 0);int len = str.size();int begin = 0;int end = 0;hashtable[str[begin]] = begin+1;int longest = end-begin+1;string longeststr=str.substr(0,1);for (int i = 1; i < len; i++){end = i;if (hashtable[str[end]] == 0||hashtable[str[end]]<begin){hashtable[str[end]] = i + 1;if (end - begin + 1>longest){longest = end - begin + 1;longeststr = str.substr(begin, longest);}}else{begin = hashtable[str[end]];hashtable[str[end]] = end + 1;}}return make_pair(longest, longeststr);}int main(){string str = "abcbak";pair<int, string> res = FindLongestSubstrNoRep(str);cout << res.first << " " << res.second << endl;}