简单的讲就是字符串不回溯。
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int countBF = 0;
int countKMP = 0;
int BF(char *A, char *a)
{
printf("\n-------BF-------\n");
int j = 0, i = 0, ispace;
printf("%s\n",A);
while(A[i] != '\0')
{
if(j<strlen(a))//a[j] != '\0')
{
if(A[i] == a[j])
{
printf("%c",a[j]);
j ++;
i ++;
countBF ++;
}
else
{
printf("%c\n",a[j]);
i = i - j +1;
j = 0;
for(ispace = 0; ispace < i; ispace++)
printf("%c",' ');
countBF ++;
}
}
if(j == strlen(a))
{
printf("\n-----------------\n");
return i - j;
}
}
printf("\n-----------------\n");
return -1;
}
int *next;
void KMP_NEXT(char *a)
{
next = malloc(sizeof(int)*(int)strlen(a));
int j = 0, i;
next[0] = next[1] = 0;
for(i = 2; i < (int)strlen(a); i++)
{
while(j > 0 && a[i-1] != a[j])
{
countKMP ++;
j = next[j];
}
if( a[j] == a[i-1] )
{
countKMP ++;
j ++;
}
next[i] = j;
}
}
int KMP(char *A, char *a)
{
printf("\n-------KMP-------\n");
printf("%s\n",A);
int i, j = 0, ispace;
for(i=0;i<strlen(A);i++)
{
while(j>0 && a[j] != A[i])
{
printf("%c\n",a[j]);
for(ispace = 0; ispace < i; ispace++)
printf("%c",' ');
j = next[j];
countKMP ++;
}
if(A[i] == a[j])
{
printf("%c",a[j]);
j++;
countKMP ++;
}
if(j == strlen(a))
{
printf("\n-----------------\n");
return i-j+1;
}
}
printf("\n-----------------\n");
return -1;
}
int main(int argc, char **argv)
{
char *A, *a;
A = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabc";
a = "aaaaaaaaaaaaabc";
printf("A(%2d): %s\n",strlen(A),A);
printf("a(%2d): %s\n",strlen(a),a);
int bf = BF(A,a);
KMP_NEXT(a);
int kmp = KMP(A,a);
printf("next(%2d):",strlen(a));
int i;
for (i=0;i<strlen(a);i++)
printf("%d,",next[i]);
printf("\n");
printf("BF pos: %d, O(%d)\n",bf,countBF);
printf("KMP pos: %d, O(%d)\n",kmp,countKMP);
return 0;
}测试字符串：
A = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabc";
a = "aaaaaaaaaaaaabc";结果：
-------BF-------
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabc
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaab
aaaaaaaaaaaaabc
-----------------
-------KMP-------
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabc
aaaaaaaaaaaaab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
ab
abc
-----------------
next(15):0,0,1,2,3,4,5,6,7,8,9,10,11,12,0,
BF pos: 30, O(435)
KMP pos: 30, O(99)测试字符串：
A = "aaaacaaaaaabaaacaaaaabcaaaaacaaa";
a = "aaaabcaaa";结果：
-------BF-------
aaaacaaaaaabaaacaaaaabcaaaaacaaa
aaaab
aaaa
aaa
aa
a
aaaab
aaaab
aaaabc
aaaa
aaa
aa
a
aaaa
aaa
aa
a
aaaab
aaaabcaaa
-----------------
-------KMP-------
aaaacaaaaaabaaacaaaaabcaaaaacaaa
aaaab
a
a
a
aaaab
ab
abc
aaaa
a
a
aaaab
abcaaa
-----------------
next( 9):0,0,1,2,3,0,0,1,2,
BF pos: 17, O(65)
KMP pos: 17, O(43)参考：
https://blog.csdn.net/rrrfff/article/details/6539598
