POJ：3461-Oulipo（KMP模板题）

Oulipo

Time Limit: 1000MS Memory Limit: 65536K

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模板

#include<stdio.h>

#include<string>

#include<cstring>

#include<iostream>

using namespace std;

const int maxn = 1e4+100;

char s1[maxn],s2[1000100];

int next[maxn];

void cal_next()//获得next数组

{

    int k;

    k = next[0] = -1;

    int len = strlen(s1);

    for(int i=1;i<len;i++)

    {

        while(k>-1 && s1[i] != s1[k+1])

            k = next[k];

        if(s1[i] == s1[k+1])

            k++;

        next[i] = k;

    }

}

int KMP()

{

    int ans = 0;

    int len = strlen(s2);

    int k = -1;

    int len1 = strlen(s1);

    for(int i=0;i<len;i++)

    {

        while(k>-1 && s1[k+1] != s2[i])

            k = next[k];

        if(s1[k+1] == s2[i])

            k++;

        if(k == len1-1)

        {

            ans++;

            k = next[k];

        }

    }

    return ans;

}

int main()

{

    int t;

    scanf("%d",&t);

    while(t--)

    {

        scanf("%s%s",s1,s2);

        cal_next();

        int ans = KMP();

        printf("%d\n",ans);

    }

    return 0;

}

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