HDU 1686 Oulipo / POJ 3461 Oulipo / SCU 2652 Oulipo （字符串匹配，KMP）

HDU 1686 Oulipo / POJ 3461 Oulipo / SCU 2652 Oulipo （字符串匹配，KMP）

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

Http

HDU:https://vjudge.net/problem/HDU-1686
POJ:https://vjudge.net/problem/POJ-3461
SCU:https://vjudge.net/problem/SCU-2652

Source

字符串匹配，KMP

解决思路

直接运用KMP算法解题，请看我的这篇文章。

代码

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

const int maxN=10001;
const int maxM=1000001;
const int inf=2147483647;

int n,m;
char W[maxN];
char T[maxM];
int F[maxN];

int main()
{
	int TT;
	cin>>TT;
	for (int ti=1;ti<=TT;ti++)
	{
		scanf("%s",W);
		scanf("%s",T);
		n=strlen(W);
		m=strlen(T);
		F[0]=-1;
		for (int i=1;i<n;i++)
		{
			int j=F[i-1];
			while ((W[j+1]!=W[i])&&(j!=-1))
			    j=F[j];
			if (W[j+1]==W[i])
			    F[i]=j+1;
			else
			    F[i]=-1;
		}
		int i=0,j=0;
		int Ans=0;
		while (i<m)
		{
			if (W[j]==T[i])
			{
				i++;
				j++;
				if (j==n)
				{
					Ans++;
					j=F[j-1]+1;
				}
			}
			else
			if (j==0)
				i++;
			else
				j=F[j-1]+1;
		}
		cout<<Ans<<endl;
	}
	return 0;
}