Oulipo 模式匹配问题

Oulipo
Time Limit:1000MS Memory Limit:65536K
Total Submit:29 Accepted:17
Description
The French author Georges Perec (1936–1982) once wrote a book, La disparition, without the letter 'e'. He was a member of the Oulipo group. A quote from the book:

Tout avait Pair normal, mais tout s’affirmait faux. Tout avait Fair normal, d’abord, puis surgissait l’inhumain, l’affolant. Il aurait voulu savoir où s’articulait l’association qui l’unissait au roman : stir son tapis, assaillant à tout instant son imagination, l’intuition d’un tabou, la vision d’un mal obscur, d’un quoi vacant, d’un non-dit : la vision, l’avision d’un oubli commandant tout, où s’abolissait la raison : tout avait l’air normal mais…

Perec would probably have scored high (or rather, low) in the following contest. People are asked to write a perhaps even meaningful text on some subject with as few occurrences of a given “word” as possible. Our task is to provide the jury with a program that counts these occurrences, in order to obtain a ranking of the competitors. These competitors often write very long texts with nonsense meaning; a sequence of 500,000 consecutive 'T's is not unusual. And they never use spaces.

So we want to quickly find out how often a word, i.e., a given string, occurs in a text. More formally: given the alphabet {'A', 'B', 'C', …, 'Z'} and two finite strings over that alphabet, a word W and a text T, count the number of occurrences of W in T. All the consecutive characters of W must exactly match consecutive characters of T. Occurrences may overlap.

Input
The first line of the input file contains a single number: the number of test cases to follow. Each test case has the following format:

One line with the word W, a string over {'A', 'B', 'C', …, 'Z'}, with 1 ≤ |W| ≤ 10,000 (here |W| denotes the length of the string W).
One line with the text T, a string over {'A', 'B', 'C', …, 'Z'}, with |W| ≤ |T| ≤ 1,000,000.

Output
For every test case in the input file, the output should contain a single number, on a single line: the number of occurrences of the word W in the text T.

Sample Input

3
BAPC
BAPC
AZA
AZAZAZA
VERDI
***ERDXIVYERDIAN

Sample Output

1
3
0

Source
BAPC 2006 Qualification



经典KMP，顺便写个模板

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

char t[1000001],p[10001];
int next[10001];

void getnext(char p[])
{
	int len = strlen(p);
	next[1] = 0;
	int q;
	int k = 0;
	for(q = 2; q <= len; q++)
	{
		while(k > 0 && p[k] != p[q - 1])k = next[k];
		if(p[k] == p[q - 1])k++;
		next[q] = k;
	}
}

int KMP(char t[],char p[])//find p in t
{
	int ans = 0;
	int i;
	int n=strlen(t);
	int m = strlen(p);
	if(n == 1 && m == 1)
	{
		if(t[0] == p[0])return 1;
		else return 0;
	}
	getnext(p);
	int q = 0;
	for(i = 0;i < n; i++)
	{
		while(q > 0 && p[q] != t[i])
			q = next[q];
		if(p[q] == t[i])q++;
		if(q == m)
		{
			ans++;
			q = next[q];
		}
	}
	return ans;
}

int main()
{
	int T;
	scanf("%d",&T);
	getchar();
	while(T--)
	{ 
		scanf("%s%s",p,t);//find p in t
		printf("%d/n",KMP(t,p));
	}
	return 0;
}