poj 3461 kmp算法

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 12500		Accepted: 4971

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

#include<stdio.h>
#include<string.h>
char str1[10005], str2[1000005];
int num, pre[10005];
void prekmp()
{
    int i, j = -1, n = strlen(str1);
    pre[0] = -1;
    for(i = 1;i < n; i++)
    {
        while(j > -1 && str1[j+1] != str1[i])
        j = pre[j];
        if(str1[j+1] == str1[i])
        j++;
        pre[i] = j;
    }
}
void kmp()
{
    int i,n,m,k;
    n = strlen(str2);
    m = strlen(str1);
    for(k = -1, i = 0; i < n; i++)
    {
        while(k > -1 && str1[k+1] != str2[i])
        k = pre[k];
        if(str1[k+1] == str2[i])
        k++;
        if(k == m-1)
        {
            num++;
            k = pre[k];
        }

    }
}
int main()
{
    int n;
    char c1, c2;
    scanf("%d",&n);
    while(n--)
    {
        scanf("%s%c%s%c",str1,&c1,str2,&c2);
        num = 0;
        prekmp();
        kmp();
        printf("%d\n",num);
    }
    return 0;
}