HDU 1686 子序列

Oulipo

 

Problem 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

 

KMP 求是否是子串

若是，求其他出現的次數

#include <iostream>
#include <algorithm>
using namespace std;
int down[11111],num;//down 表示下一個
char a[1111111],b[11111];
int n,m;
void  getnext()
{
	int i,j;
	i=0,down[0]=-1,j=-1;
	while(i<m)
	{
		if(j==-1||b[i]==b[j])
		{
			i++,j++;
			if(b[i]==b[j])
				down[i]=down[j];
			else down[i]=j;
		}
		else
			j=down[j];
	}
}
int kmp()
{
	int i,j;
	i=j=num=0;
	while(i<n)
	{
		if(a[i]==b[j]||j==-1)
			i++,j++;
		else
			j=down[j];
		if(j==m)
			num++,j=down[j];
	}
	return num;
}
int main()
{
	int t;
	while(~scanf("%d",&t))
	{
		getchar();
		while(t--)
		{
			gets(b);
			gets(a);
			n=strlen(a);
			m=strlen(b);
			getnext();
			printf("%d\n",kmp());
		}
	}
	return 0;
}