POJ 题目3461 Oulipo（KMP）

Oulipo

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

ac代码

<pre name="code" class="cpp">#include<stdio.h>
#include<string.h>
#include<stdlib.h>
char s1[100100],s2[1000100];
int next[1000100];
void getnext(char *s)
{
	int len=strlen(s);
	int i,j;
	i=0;j=-1;
	next[0]=-1;
	while(i<=len)
	{
		if(j==-1||s[i]==s[j])
		{
			i++;
			j++;
			next[i]=j;
		}
		else
			j=next[j];
	}
}
int kmp(char *s1,char *s2)
{
	int len1=strlen(s1);
	int len2=strlen(s2);
	memset(next,0,sizeof(next));
	getnext(s1);
	int i,j,ans;
	i=j=ans=0;
	while(j<=len2)
	{
		if(i==-1||s1[i]==s2[j])
		{
			i++;
			j++;
		}
		else
			i=next[i];
		if(i==len1)
		{
			ans++;
			i=next[i];
		}
	}
	return ans;
}
int main()
{
	int t;
	scanf("%d",&t);
	while(t--)
	{
		scanf("%s",s1);
		scanf("%s",s2);
		printf("%d\n",kmp(s1,s2));
	}
}