寒假训练--KMP--poj3461Oulipo

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 19729		Accepted: 7920

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

经典的KMP的题，寻找一个字串出现的次数，并且母串中的子串有重叠，在用KMP求出子串的next后，开始查找，当找到符合的位置时，不要退出，而是将i =  next[i]；继续遍历 计数。    

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char str1[10002] , str2[1000002] ;
int next[10002] ;
void getnext()
{
    int j = 0 , k = -1 , l ;
    next[0] = -1 ;
    l = strlen(str1);
    while(j < l )
    {
        if(k==-1 || str1[j]== str1[k])
        {
            k++;
            j++;
            next[j] = k ;
        }
        else
            k = next[k];
    }
}
int main()
{
    int k , m , i , j , count ;
    scanf("%d", &m);
    for(k = 1 ; k <= m ; k++)
    {
        scanf("%s%s", str1, str2);
        getnext();
        i = 0 ; j = 0 ; count = 0;

        while(str2[j] !='\0')
        {
            if(str1[i]==str2[j])
            {
                i++; j++;
            }
            else
            {
                if(next[i]==-1)
                {
                    i = 0 ;
                    j++;
                }
                else
                {
                    i = next[i];
                }
            }
            if(str1[i]=='\0')
            {
                count++;
                i = next[i] ;
            }
        }
        printf("%d\n", count);
    }
}