3. 无重复字符的最长子串

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int len = 0;
        int left = 0, right = 0;
        unordered_map<char, int> hash_map;
        while(right<s.size())
        {
            if(!hash_map[s[right]])
            {
                hash_map[s[right]]++;
                 if(right-left+1>len)
                    len = right-left+1;
            }
            else
            {
                while(hash_map[s[right]]&&left<=right)
                     hash_map[s[left++]]--;

                hash_map[s[right]]++;
               
            }
            right++;

        }
        return len;

    }
};