字符串匹配算法实现

KMP算法

 1 void Next(char *src,int n,int *next)
 2 {
 3 int j,k;
 4 j=0;
 5 k=-1;
 6 next[0] = -1;
 7 while(j<n-1)
 8 {
 9 if(k==-1 || src[j] == src[k])
10 {
11 ++k;++j;
12 next[j] = k;
13 }
14 else
15 k=next[k];
16 }
17 }
18 
19 int KMP(char *des,int n ,char *src,int m)
20 {
21 assert(des != NULL && src !=NULL && n>0 && m>0);
22 
23 char *pdes=des;
24 char *psrc=src;
25 
26 int i=0,j=0;
27 int *next = (int *)malloc(m*sizeof(int));
28 Next(src,m,next);
29 for(int k = 0;k<m;k++)
30 printf("%d ",next[k]);
31 printf("\n");
32 
33 while(j<m && i<n)
34 {
35 if(j==-1 || psrc[j] == pdes[i])
36 {
37 ++i;++j;
38 }
39 else
40 {
41 j=next[j];
42 }
43 }
44 if(j<m)
45 return -1;
46 else
47 return i-j;
48 }

BF算法

 1 int BF(const char *des,const char *src)
 2 {
 3 assert(des != NULL && src != NULL);
 4 int i,j;
 5 int len_1 = strlen(des);
 6 int len_2 = strlen(src);
 7 if(len_1 < len_2)
 8 return -1;
 9 for(i = 0;i<=len_1-len_2;i++)
10 {
11 for(j=0;j<len_2;j++)
12 {
13 if(des[i+j] != src[j])
14 break;
15 }
16 if(j==len_2)
17 return i;
18 }
19 return -1;
20 }