KMP POJ-3461 Oulipo

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 26246		Accepted: 10475

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
AVERDXIVYERDIAN

Sample Output

1
3
0

Source

BAPC 2006 Qualification

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

void get_next(char* p, int next[])
{
	int k = -1;
	int j = 0;
	next[0] = -1;
	int len = strlen(p);
	while (j < len)
	{
		if (k == -1 || p[j] == p[k])
		{
			j++;
			k++;
			if (p[j] != p[k])
			{
				next[j] = k;
			}
			else
			{
				next[j] = next[k];
			}
		}
		else
		{
			k = next[k];
		}
	}
}

int kmp(char* p, char* t, int next[])
{
	int ans = 0;
	int plen = strlen(p);
	int tlen = strlen(t);
	int i = 0, j = 0;
	while (i < tlen)
	{
		if (j == -1 || p[j] == t[i])
		{
			i++;
			j++;
		}
		else
		{
			j = next[j];
		}
		if (j == plen)
		{
			ans++;
			j = next[j];
		}
	}
	return ans;
}
char t[1000010], p[1000010];
int next[1000010];
int main()
{
	int n;
	scanf("%d", &n);
	while (n--)
	{
		scanf("%s", p);
		scanf("%s", t);
		get_next(p, next);
		int ans = kmp(p, t, next);
		printf("%d\n", ans);
	}
	return 0;
}