剑指offer48 最长不含重复字符的子字符串[C++]

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        if(!s.length()) return 0;
        vector<int> index(256,0);
        int maxLen = 0, n = s.length();
        for (int j = 0, i = 0; j < n; j++) {
            i = max(index[s[j]],i);
            maxLen = max(maxLen, j - i + 1);
            index[s[j]] = j + 1; 
        }
        return maxLen;
    }
};

　　加1是为了从重复元素的下一个开始计算