POJ 3461 Oulipo（KMP统计子串出现次数）

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 12818		Accepted: 5128

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

Source

BAPC 2006 Qualification

 

 

 

 

典型的KMP

 

统计模式串在主串中出现的次数

 

#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;
char W[10010],T[1000010];
int wlen,tlen;
int next[10010];
void getNext()
{
    int j,k;
    j=0;
    k=-1;
    next[0]=-1;
    while(j<wlen)
    {
        if(k==-1||W[j]==W[k])
        {
            next[++j]=++k;
        }
        else k=next[k];
    }
}
int KMP_count()
{
    int ans=0;
    int i,j=0;
    if(wlen==1&&tlen==1)
    {
        if(W[0]==T[0])return 1;
        else return 0;
    }
    getNext();
    for(i=0;i<tlen;i++)
    {
        while(j>0&&T[i]!=W[j])
          j=next[j];
        if(W[j]==T[i])j++;
        if(j==wlen)
        {
            ans++;
            j=next[j];
        }
    }
    return ans;
}
int main()
{
  //  freopen("in.txt","r",stdin);
   // freopen("out.txt","w",stdout);
    int tcase;
    scanf("%d",&tcase);
    while(tcase--)
    {
        scanf("%s%s",&W,&T);
        wlen=strlen(W);
        tlen=strlen(T);

        printf("%d\n",KMP_count());
    }
    return 0;
}