leetcode--Longest Substring Without Repeating Characters

1.问题

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.

2.分析

用sub保存当前最大的没有重复的子字符串。取当前字符时，只有两种可能：(1)跟sub字符串前面某个字符重复，那么就要把sub字符串的第0位开始到第一个重复字符之间的所有字符删掉，再把重复字符加到sub后面；(2)跟sub字符串所有字符不重复，当前字符加到sub后面。

贪心策略是，sub子字符串的当前长度大于最大子长度的话，更新最大子长度。

3.

class Solution {public:    int lengthOfLongestSubstring(string s) {        int maxLen=0,curLen=0;        string sub = "";        for(auto c:s) {            int postion = sub.find(c);            if(postion!=sub.npos) {                sub.erase(0,postion+1);                curLen = curLen - (postion+1);            }            sub += c;            curLen++;            maxLen = max(maxLen,curLen);        }        return maxLen;    }};