【剑指offer】【字符串】48. 最长不含重复字符的子字符串

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        unordered_map<char, int> hash;
        int res = 0;
        for(int i = 0, j = 0; j < s.size(); j++)
        {
            if(++hash[s[j]] > 1)
            {
                while(i < j)
                {
                    hash[s[i]]--;
                    i++;
                    if(hash[s[j]] == 1) break;
                }
            }
            res = max(res, j- i + 1);
        }
        return res;
    }
};