LeetCode 28. Implement strStr()

 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 
 5 class Solution {
 6 public:
 7     int strStr(string haystack, string needle) 
 8     {
 9         // Corner case
10         if (needle.empty()) return 0;
11         if (haystack.empty()) return -1;
12         
13         int n = haystack.length() - needle.length() + 1;
14 
15         // better use < rather than <=
16         for (int i = 0; i < n; i ++)
17         {
18               bool flag = true;
19               
20               for (int j = 0; j < needle.length(); j ++)
21               {
22                   if (haystack.at(i + j) != needle.at(j))
23                   {
24                     flag = false;
25                     break;
26                   }
27               }
28               
29               if (flag) 
30                  return i;
31         }
32         
33         return -1;
34     }    
35 };
36 
37 int main ()
38 {
39     Solution testSolution;
40     string s1 = "mississippi";
41     string s2 = "issi";
42     
43     cout << testSolution.strStr(s1, s2) << endl;
44     
45     getchar();
46     
47     return 0;
48 }