常见算法:最长子串

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int startIndex = 0;
        int res = 0;
        map<char,int> charMap;
        for (int i = 0; i < s.length(); i++) {
            char tmp = s.at(i);
            if (charMap.find(tmp) != charMap.end()) {
                // 重新记录下标位置
                startIndex = max(startIndex, charMap[tmp] + 1);
            }
            charMap[tmp] = i;
            res = max(res, i - startIndex  +1);

        }

        return res;

    }
};