Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb" Output: 3 Explanation: The answer is ​​"abc"​​, with the length of 3.

Example 2:

Input: "bbbbb" Output: 1 Explanation: The answer is ​​"b"​​, with the length of 1.

Example 3:

Input: "pwwkew" Output: 3 Explanation: The answer is ​​"wke"​​, with the length of 3. Note that the answer must be a substring, ​​"pwke"​​ is a subsequence and not a substring.

题解：

动态记录上一次不重复点

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int prev = -1, res = 0;
        int len = s.length();
        vector<int> idx(200, -1);
        for (int i = 0; i < len; i++) {
            if (idx[s[i]] != -1) {
                prev = max(prev, idx[s[i]]);
            }
            res = max(res, i - prev);
            idx[s[i]] = i;
        }
        return res;
    }
};