//! n^2,n -> 双重循环耗时n^2;hash表最多占地n
class Solution {
public:
  int lengthOfLongestSubstring(string s) {
    int res = 0;
    for (int i = 0; i < s.length(); ++i) {
      unordered_set<char> hashTable;
      hashTable.insert(s[i]);
      int nowLen = 1;
      for (int j = i + 1; j < s.length(); ++j) {
        if (hashTable.find(s[j]) == hashTable.end()) {
          ++nowLen;
          hashTable.insert(s[j]);
        } else {
          break;
        }
      }
      res = max(res, nowLen);
    }
    return res;
  }
};

//! n,n -> 两个指针各遍历一次共2n;hash表最多占地n
class Solution {
public:
  int lengthOfLongestSubstring(string s) {
    int res = 0;
    int left = 0;
    int right = 0;
    unordered_set<char> hashTable;

    while (right < s.length()) {
      if (hashTable.find(s[right]) == hashTable.end()) {
        // s[right]未在hashTable里时，加入hashTable，right右移
        hashTable.insert(s[right++]);
      } else {
        res = max(res, right - left);
        hashTable.erase(s[left++]);
      }
    }
    res = max(res, right - left);
    return res;
  }
};