题目：

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"Output: 3 Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: "bbbbb"Output: 1Explanation: The answer is "b", with the length of 1.

Example 3:

Input: "pwwkew"Output: 3Explanation: The answer is "wke", with the length of 3.              Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

代码(C++实现)：

1 class Solution { 2 public: 3     int lengthOfLongestSubstring(string s)  4     { 5         // 定义一个map用来存放整个字符串s 6         unordered_map
        
          unmap; 7          8         // tempLength记录每次扫描位置开始的一次统计的最长字符串的长度 9         int tempLength = 0;10         // 众多tempLength中的最大值11         int maxLength = 0;12         13         // 第一层循环：分别以s中的每个字符为基准，进行遍历14         for (int j = 0; j < s.size(); j++)15         {16             // 第二层循环：以当前第一层循环中当前的字符为基准，进行遍历，统计以此字符为基准的tempLength17             for (int i = j; i < s.size(); i++)18             {19                 // 是否tempLength继续增加的条件是，map中没有出现过当前指向的字符20                 if (unmap.count(s[i]) == 0)                21                 {22                     pair
         
           myshopping(s[i], i);23                     // 如果当前的map中无此字符，将当前字符插入到map中24                     unmap.insert(myshopping);25                     tempLength++;26                     maxLength = maxLength > tempLength ? maxLength : tempLength;27                 }28                 // 当前字符已经在map中了，直接break，并将本次使用的map进行清除操作29                 else30                 {31                     32                     tempLength = 0;33                     unmap.clear();34                     break;35                 }36 37             }38         }39     40         return maxLength;41         }42 };