代码

 1 #include <iostream>
 2 #include <string>
 3 #include <typeinfo>
 4 #include <vector>
 5 using namespace std;
 6 
 7 int KMP(const string &pattern,const string &str)
 8 {
 9     const int len1 = pattern.length();
10     const int len2 = str.length();
11     vector<int> next(len1);
12     next[0]=0;
13     int i,j,k;
14     for (i=1;i<len1;i++)
15     {
16         k=next[i-1];
17         while (pattern[i] != pattern[k]&&k!=0)
18         {
19             k=next[k-1];
20         }
21         if(pattern[i] == pattern[k])
22             next[i]=k+1;
23         else
24             next[i]=0;
25     }
26     i=j=0;
27     int mycount=0;
28     while (j < len2)
29     {
30         if (pattern[i]!=str[j])
31         {
32             if (i==0)
33             {
34                 i=0;
35                 j++;
36             }
37             else
38                 i=next[i-1];
39         }
40         else
41         {
42             i++;
43             j++;
44             if(pattern[i] == '\0')
45             {
46                 mycount++;
47                 i=next[len1-1];//为什么取pattern最后一个字符的next，自己想
48                 //i赋值位next[len1-1]是为了防止j回溯
49             }
50         }
51     }
52 
53     return mycount;
54 }
55 
56 int main()
57 {
58     int n;
59     string pattern,str;
60     while (cin >> n)
61     {
62         while (n--)
63         {
64             cin >> pattern >> str;
65             cout << KMP(pattern,str)<<endl;
66         }
67     }
68     return 0;
69 }