朴素的匹配算法：

#include<iostream>
#include<string>
using namespace std;
void Match(string longstr,string shortstr)
{

	string::iterator i,j,temp;
	i=longstr.begin();
	temp=i;
	j=shortstr.begin();
	while(i!=longstr.end()&&j!=shortstr.end())
	{
		if(*i==*j)
		{
			++i;
			++j;
		}
		else{
			++temp;
			i=temp;
			j=shortstr.begin();
		}
	}
	if(j==shortstr.end())
		cout<<"匹配"<<endl;
	else
		cout<<"不匹配"<<endl;
	return 0;
} 

KMP算法：

#include<iostream>
#include<string>
using namespace std;
void getNext(string shortstr,int *next)
{
    int j,k;
    next[0]=-1;
    j=0;
    k=-1;
	while(j<shortstr.size())
    {
        if(k==-1||shortstr[j]==shortstr[k])    //匹配的情况下,shortstr[j]==shortstr[k]
        {
            j++;
            k++;
            next[j]=k;
        }
        else                   //shortstr[j]!=shortstr[k]
            k=next[k];
    }
}
int KMPMatch(string longstr,string shortstr)
{
    int next[100];
    int i,j;
    i=0;
    j=0;
    getNext(shortstr,next);
	while(i<longstr.size())
    {
        if(j==-1||longstr[i]==shortstr[j])
        {
            i++;
            j++;
        }
        else
        {
            j=next[j];       //消除了指针i的回溯
        }
		if(j==shortstr.size())
            return i-shortstr.size();//返回匹配的初始下标
    }
    return -1;
}