KMP

#include <iostream>
using namespace std;

int KMPIndexHelp(const string &T,const string &P,int pos,int next[])
{
	int i=pos,j=0;
	while(i<T.length()&&j<P.length())
	{
	//	cout<<"111"<<endl;
		if(j==-1)
		{
			i++;
			j=0;
		}else if(P[j]==T[i])
		{
			cout<<"j="<<j<<"i="<<i<<endl;
			i++;
			j++;
		}else
		{
			j=next[j];
			cout<<"j="<<j<<endl;
		}
	}
	cout<<"j="<<j<<endl;
	cout<<"P.length()="<<P.length()<<endl;
	if(j<0&&P.length()>=0||j<P.length())
	{
		return -1;
	}
	else
	{
		return i-j;
	}
		
}

void getNext(const string &P,int next[])
{
	int j=0,k=-1;
	next[0]=-1;
	while(j<P.length()-1)//應爲遞推
	{
	//	cout<<next[j]<<endl;
	//	cout<<j<<endl;
		if(k==-1)
		{
			//cout<<"333"<<endl;
			next[j+1]=0;
			j++;
			k=0;
		}else if(P[j]==P[k])
		{
			next[j+1]=k+1;
			k++;
			j++;
		}else
			k=next[k];
	}
}

int KMPIndex(const string &T,const string &P,int pos=0)
{
	int *next=new int[P.length()];
	getNext(P,next);
	int result=KMPIndexHelp(T,P,pos,next);
	delete []next;
	return result;
}
void main()
{
	cout<<KMPIndex("abbababa","abc",0)<<endl;
}