HDU - 1686 Oulipo

https://vjudge.net/problem/HDU-1686

HDU - 1686 Oulipo

• • 题目
  • 分析
  • AC代码

题目

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

分析

简单的kmp应用

AC代码

#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int N=1e6+10;
int n,m,t;
int ne[N];
char s[N],p[N];
int main()
{
	cin>>t;
	while(t--)
	{
		scanf("%s",p);
		scanf("%s",s);
		
		n=strlen(s);
		m=strlen(p);
		
		ne[0]=-1;
		for(int i=0,j=-1;i<=m;)
		{
			if(j==-1 || p[i]==p[j])
			{
				i++,j++;
				ne[i]=j;
			}
			else
				j=ne[j];
		}
		
		int ans=0;
		for(int i=0,j=0;i<n;)
		{
			if(j==-1 || s[i]==p[j])
			{
				i++;j++;
			}
			else
				j=ne[j];
			
			if(j==m)
				ans++;			
		}
		cout<<ans<<endl;
	}
	return 0;
}