ＫＭＰ poj 3461

    找一个模式串在主串中出现的次数

#include <iostream>
#include <cstring>

using namespace std;

const int MAXN = 1000010;
const int MAXM = 10010;

int nextval[MAXM];

void Get_NextVal(char* str)
{
	int len = strlen( str );
	int i = 0, j = -1;
	nextval[0] = -1;
	while (i < len)
	{
		if (j == -1 || str[i] == str[j])
		{
			++i;
			++j;
			if(str[i] == str[j])
				nextval[i] = nextval[j];
			else
				nextval[i] = j;
		}
		else
			j = nextval[j];
	}
}


int KMP(char* str1, char* str2)
{
	int i = 0, j = 0;
	int ans = 0;
	int len1 = strlen(str1);
	int len2 = strlen(str2);
	Get_NextVal(str1);
	while (i < len2)
	{
		if (j == -1 || str1[j] == str2[i])
		{
			++i;
			++j;
		}
		else
			j = nextval[j];
		if(j >= len1)
		{
			ans++;
			j = nextval[j];//这里不是从模式串的首部从新开始，而是从他的nextval开始
		}
	}
	return ans;
}


int main()
{
	int T;
	cin>>T;
	char str1[MAXM], str2[MAXN];
	while (T--)
	{
		cin>>str1;
		cin>>str2;
		int sum = 0;
		sum = KMP(str1, str2);
		cout<<sum<<endl;
	}
	return 0;
}