KMP算法 hdu4686 Oulipo

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

 #include <stdio.h>
#include <string.h>

int next[];
char str1[],str2[];
int cnt;

void get_next(int len2)//生成next数组
{
    int i = ,j = -;
    next[] = -;
    while (i<len2)
    {
        if(j == - || str2[i] == str2[j])
        {
            i++;
            j++;
            if (str2[i]!=str2[j])
                next[i] = j;
            else
                next[i] = next[j];
        }
        else
            j = next[j];
    }
}

int kmp(int len1,int len2)//kmp算法
{
    int i=,j=;
    get_next(len2);
    while(i<len1)
    {
        if(j==-||str1[i]==str2[j])
        {
            ++i;
            ++j;
        }
        else
            j=next[j];
        if(j == len2)
        {
            cnt++;
            j = next[j];
        }
    }
}

int main()
{
    int n;
    int len1,len2;
    scanf("%d",&n);
    getchar();
    while(n--)
    {
        gets(str2);
        gets(str1);
        len1 = strlen(str1);
        len2 = strlen(str2);
        cnt = ;
        kmp(len1,len2);
        printf("%d\n",cnt);
    }
    return ;
}