KMP-模板

#include <iostream>
#include <string>
using namespace std;

const int maxn=1000005;
char A[maxn],B[maxn];  //main string A & model string B
int next[maxn]; 
int n,m;              //the length of string A & string B

void Get_next(char *B,int next[])
{
	next[1]=0;
	int j=0;
	for(int i=2;i<=m;i++)
	{
		while((j>0)&&(B[j+1]!=B[i])) 
			j=next[j];
		if(B[j+1]==B[i]) 
			j++;
		next[i]=j;
	}     
}

void KMP()
{
	int j=0;
	for(int i=1;i<=n;i++)
	{
		while((j>0)&&(B[j+1]!=A[i])) 
			j=next[j];
		if(B[j+1]==A[i]) 
			j++;
		if(j==m)
		{
			cout<<"match position: "<<i-m<<endl;
			j=next[j];
		}
	}        
}

int main()
{
	while (cin>>A+1>>B+1)
	{
		n=strlen(A+1);
		m=strlen(B+1);
		cout<<"A="<<A+1<<" B="<<B+1<<endl;
		Get_next(B,next);
		for(int i=1;i<=m;i++)
			cout<<"next["<<i<<"]="<<next[i]<<endl;
		KMP();
	}
}