4.7 记录

　　

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int m[256] = {0}, res = 0, left = 0;
        for (int i = 0; i < s.size(); ++i) {
            if (m[s[i]] == 0 || m[s[i]] < left) {
                res = max(res, i - left + 1);
            } else {
                left = m[s[i]];
            }
            m[s[i]] = i + 1;
        }
        return res;
    }
};

m[s[i]中是s[i]应该是字符，m[char]也能够运行吗？是不是string类的特殊用法？