双指针：判断子序列

 1     bool isSubsequence(char * s, char * t)
 2     {
 3         int j = 0,i = 0;
 4         int lens = strlen(s);
 5         int lent = strlen(t);
 6         while(i < lens && j < lent)
 7         {
 8             if(s[i] == t[j])
 9             {
10                 i++;
11                 j++;
12             }
13             else
14             {
15                 j++;
16             }
17         }
18         if(i == lens)
19         {
20             return true;
21         } 
22         else
23         {
24             return false;
25         }
26     }