3. Longest Substring Without Repeating Characters

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.

 

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int count=0;
        vector<int> table(128,-1);
        //要利用j将起始位置更新到第一次出现重复的位置。
        int j=0;
        for(int i=0;i<s.size();i++)
        {
            
            if(table[s[i]]!=-1)
            {
                while(j<=table[s[i]]) table[s[j++]]=-1;
            }
            count=max(count,i-j+1);
            table[s[i]]=i;
        }
        return count;
    }
};