【LC】3. 无重复字符的最长子串

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题目描述

题解

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int len = s.size();
        if (len == 0) return 0;
        //保存字符
        unordered_set<char> usc;
        int maxlen = 0;
        int mark = -1;
        for (int i = 0; i < len; ++i)
        {
            if (i != 0)
            {
                usc.erase(s[i - 1]);
            }
            //该字符未插入unordered_set
            while (mark + 1 < len && !usc.count(s[mark + 1]))
            {
                usc.insert(s[mark + 1]);
                ++mark;
            }
            maxlen = max(maxlen, mark - i + 1);
        }
        return maxlen;
    }
};