【LeetCode刷题系列 - 003题】Longest Substring Without Repeating Characters

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

Example 3:

Input: "pwwkew"
Output: 3
Explanation: 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)：

 class Solution {
 public:
     int lengthOfLongestSubstring(string s)
     {
         // 定义一个map用来存放整个字符串s
         unordered_map<char, int> unmap;

         // 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
         int tempLength = ;
         // 众多tempLength中的最大值
         int maxLength = ;

         // 第一层循环：分别以s中的每个字符为基准，进行遍历
         for (int j = ; j < s.size(); j++)
         {
             // 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tempLength
             for (int i = j; i < s.size(); i++)
             {
                 // 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
                 if (unmap.count(s[i]) == )
                 {
                     pair<char, int> myshopping(s[i], i);
                     // 如果当前的map中无此字符，将当前字符插入到map中
                     unmap.insert(myshopping);
                     tempLength++;
                     maxLength = maxLength > tempLength ? maxLength : tempLength;
                 }
                 // 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
                 else
                 {

                     tempLength = ;
                     unmap.clear();
                     break;
                 }

             }
         }

         return maxLength;
         }
 };