【leetcode】Longest Substring Without Repeating Characters

 1 class Solution {
 2 public:
 3     int lengthOfLongestSubstring(string s) {
 4        
 5         map<char,int> char2index;
 6        
 7         int start_index=0;
 8         int result=0;
 9         int i;
10         for(i=0;i<s.length();i++)
11         {
12             //从来没有出现过的元素
13             if(char2index.find(s[i])==char2index.end())
14             {
15                 char2index[s[i]]=i;
16             }
17             else
18             {
19                 //出现过，且在start_index之后出现
20                 if(char2index[s[i]]>=start_index)
21                 {
22                     result=max(result,i-start_index);
23                     start_index=char2index[s[i]]+1;
24                     char2index[s[i]]=i;
25                 }
26                 else
27                 {
28                     //在start_index之前出现
29                     char2index[s[i]]=i;
30                 }
31  
32             }
33         }
34         result=max(result,i-start_index);
35        
36         return result;
37     }
38 };

 1 class Solution {
 2 public:
 3     int lengthOfLongestSubstring(string s) {
 4        
 5         map<char,int> char2index;
 6        
 7         int start_index=0;
 8         int result=0;
 9         int i;
10         for(i=0;i<s.length();i++)
11         {
12             if(char2index.find(s[i])!=char2index.end()&&char2index[s[i]]>=start_index)
13             {
14                 result=max(result,i-start_index);
15                 start_index=char2index[s[i]]+1;
16             }
17             char2index[s[i]]=i;
18         }
19        
20         result=max(result,i-start_index);
21        
22         return result;
23     }
24 };