HDU 1686 Oulipo

題目

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

代碼：

#include <iostream>
#include <string.h>
#include <stdio.h>
#define a 10000001
using namespace std;
int next[a],cnt;
char s[a],p[a];
void getnext(int len)
{
    next[0]=-1;
    int j=0;
    int k=-1;
    while(j<len-1)
    {
        if((k==-1)||(p[j]==p[k]))
        {
            j++;
            k++;
            if(p[j]!=p[k])
                next[j]=k;
            else
                next[j]=next[k];
        }
        else
            k=next[k];
    }
}
void kmp(int slen,int plen)
{
    int i=0,j=0;
    getnext(plen);
    while (i<slen)
    {
        if(j==-1||s[i]==p[j])
        {
            i++;
            j++;
        }
        else
        {
            j=next[j];
        }
        if(j==plen)
         {
             cnt++;
             j=next[j];
         }
    }
}

int main()
{
    int n,slen,plen;
    cin>>n;
    getchar();
    while(n--)
    {
        gets(p);
        gets(s);
        slen=strlen(s);
        plen=strlen(p);
        cnt=0;
        kmp(slen,plen);
        cout<<cnt<<endl;
    }
    return 0;
}

知識點：

KMP

http://blog.csdn.net/v_july_v/article/details/7041827