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最新推荐文章于 2021-12-11 18:48:23 发布

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本文介绍了一个字符串匹配问题，旨在快速计算给定单词在一个长文本中出现的次数，包括算法实现及样例输入输出。

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Oulipo

Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 16442 Accepted Submission(s): 6565

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

这个和 http://blog.youkuaiyun.com/zhang__liuchen/article/details/78502308差不多。

#include <iostream>
#include <cstring>
#include <cstdio>
const int N=1e4;
const int M=1e6;
char mo[N+10];
int Next[N+10];
char str[M+10];
int len;
using namespace std;
void getNext()
{
	Next[0]=-1;
	int i=0,j=-1;
	while(i<len)
	{
		if(j==-1||mo[i]==mo[j])
		{
			i++;
			j++;
			Next[i]=j;
		}
		else
			j=Next[j];
	}
}
int main()
{
	int T;
	scanf("%d",&T);
	while(T--)
	{
		scanf("%s%s",mo,str);
		len=strlen(mo);
		getNext();
		int ans=0;
		int i=0,j=0;
		int len1=strlen(str);
		while(i<len1)
		{
			if(j==-1||str[i]==mo[j])
			{
				i++;
				j++;
			}
			else
				j=Next[j];
			if(j==len)
				ans++;
		}
		printf("%d\n",ans);
	}
	return 0;
}