KMP算法源码实现

对于KMP算法的讲解，Matrix67在这里给出了很详细的解释，我在这里只是实现了相关源码而已，以作备用。

#include < iostream >
using namespace std;

const int * get_substring_arr( const char * sequence);
void kmp( const char * src, const char * substring, const int * a);

int main()
{
char * src = " acabaabaabcacaabc " ;
char * substring = " abaabcac " ;
kmp(src, substring, get_substring_arr(substring));
return 0 ;
}

// process the substring
const int * get_substring_arr( const char * substring)
{
int substring_len = strlen(substring);
int * a = new int [substring_len];
a[ 0 ] = - 1 ;
int j = - 1 ;
for ( int i = 1 ; i < substring_len; i ++ )
{
while (j > - 1 && substring[i] != substring[j + 1 ])
j = a[j];
if (substring[j + 1 ] == substring[i])
j = j + 1 ;
a[i] = j;
}
return a;
}

// process src & substring to get the position
void kmp( const char * src, const char * substring, const int * a)
{
int j = - 1 ;
int substring_len = strlen(substring);
int src_len = strlen(src);
for ( int i = 0 ; i < src_len; i ++ )
{
while (j > - 1 && src[i] != substring[j + 1 ])
j = a[j];
if (src[i] == substring[j + 1 ])
j ++ ;

if (j == substring_len - 1 )
{
printf( " From position %d to position %d\n " , i + 2 - substring_len, i + 1 );
j = a[j];
}
}
}