//0049最长不含重复字符的子字符串
class Solution {
public:
    int longestSubstringWithoutDuplication(string s) {
        vector<int>count(26, 0);
        int ans = 0, len = s.length();
        int l = 0, r = 0;
        while(l <= r && r < len) {
            count[s[r] - 'a']++;
            //保证字符串合法
            if (count[s[r] - 'a'] > 1) {
                while (count[s[r] - 'a'] > 1) {
                    count[s[l] - 'a']--;
                    ++l;
                }
            }
            //之前的代码在if后面的else里面加的r++，有的情况不会成立
            r++;
            ans = max(ans, r - l);
        }
        return ans;
    }
};