LeetCode3：最长不重复字串

 1 class Solution {
 2 public:
 3     int lengthOfLongestSubstring(string s) {
 4         if(s.size() == 0) return 0;
 5         unordered_set<char> lookup;
 6         int maxStr = 0;
 7         int left = 0;
 8         for(int i = 0; i < s.size(); i++){
 9             while (lookup.find(s[i]) != lookup.end()){
10                 lookup.erase(s[left]);
11                 left ++;
12             }
13             maxStr = max(maxStr,i-left+1);
14             lookup.insert(s[i]);
15     }
16         return maxStr;
17         
18     }
19 };