题解 | 最长不含重复字符的子字符串

#include <unordered_map>
class Solution {
  public:
    int lengthOfLongestSubstring(string s) {
        if (s.empty())return 0;

        unordered_map<char, int>
        log;  //记录窗口中有的字母和下标，便于检测

        int left = 0, right = 0;  //right是要验证的位置
        int maxlen = 0;
        while (left <= right && right < s.size()) {
            if (log.find(s[right]) == log.end()) {  //没炸到,不会重复
                log[s[right]] = right;
                right++;
                maxlen = max(maxlen, right - left); //更新
            } else {   //有重复
                int next_left = log[s[right]]+1;
                for(int i=left; i<next_left; i++){  //如果条件改为i<log[s[right]]+1,则无法删除log[s[right]],且不报错;
                    log.erase(s[i]);//更新hash表，逐个删除
                }
                left = next_left;
            }
        }

        return maxlen;
    }
};