KMP算法模板

 1 #include <cstring>
 2 #include <iostream>
 3 using namespace std;
 4 
 5 void get_next(const char *ptrn,int plen,int *next)
 6 {
 7     int i=0;
 8     next[i]=-1;
 9     int j=-1;
10     while(i<plen-1)
11     {
12         if(j==-1||ptrn[i]==ptrn[j])
13         {
14             ++i;
15             ++j;
16             if(ptrn[i]!=ptrn[j])
17                 next[i]=j;
18             else
19                 next[i]=next[j];
20         }
21         else
22             j=next[j];
23     }
24 }
25 
26 int kmp_search(const char *src,int slen,const char *patn,int plen,const int *next,int pos)
27 {
28     int i=pos;
29     int j=0;
30     while(i<slen&&j<plen)
31     {
32         if(j==-1||src[i]==patn[j])
33         {
34             ++i;
35             ++j;
36         }
37         else
38         {
39             j=next[j];
40         }
41     }
42     if(j>=plen)
43         return i-plen;
44     else
45         return -1;
46 }
47 
48 int main()
49 {
50     char src[]="aabcabcebafabacabceabcaefabcacdabcab";
51     char prn[]="abac";
52     int slen=strlen(src);
53     int plen=strlen(prn);
54     int* next=new int[plen];
55     get_next(prn,plen,next);
56     for(int i=0;i<plen;++i)
57         cout<<next[i]<<" ";
58     cout<<endl;
59     cout<<"result sub str: "<<kmp_search(src,slen,prn,plen,next,0)+1<<endl;
60     delete []next;
61     return 0;
62 }