数据结构之KMP算法

//对字串进行处理，得到next表
#include <stdio.h>
#define N 50005
int ans,next[N],P[N],M[N];
void GetNext(int *P){
      next[0]=-1;
      for( int i = 1,j=-1 ; P[i] ; i++ ) {
            if( P[i] == P[j+1] ){
                  j++;
                  next[i]=j;
            }
            else{
                  while( j!=-1 && P[i] != P[j+1] )
                        j=next[j];
                  next[i] = j;
            }
      }
}
void Kmp(int *M,int  *P){
      GetNext(P);
      for(int i = 0, j = -1; M[i] ; i++ ){
            while( j !=-1 && M[i] != P[j+1] )
                  j = next[j] ;
            if( j == -1 && M[i] !=P[j+1] )
                  continue;
            else
                  j++;
            if( P[ j+1 ] == 0 )
                  ans++;
      }
}