【KMP】Oulipo

KMP算法

求串内匹配数，计数时返回next[]位置。

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

Source

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 1 #include<stdio.h>

 2 #include<memory.h>

 3 #include<string.h>

 4 char a[10001],b[1000001];

 5 int Next[10001];

 6 void getn(int s){

 7     int i=0,j=-1;

 8     memset(Next,0,sizeof(Next));

 9     Next[0]=-1;

10     while(i<s){

11         if(j==-1||a[i]==a[j]){

12             i++;

13             j++;

14             Next[i]=j;

15         }

16         else j=Next[j];

17     }

18 }

19 int getnum(int x,int y){

20     int i=0,j=0,k=0;

21     while(i<y&&j<x){    //j<x避免死循环

22         if(j==-1||b[i]==a[j]){ i++; j++; }

23         else j=Next[j];

24         if(j==x){

25             k++;

26             j=Next[j];    //返回对应next[]位置

27         }

28     }

29     return k;

30 }

31 int main()

32 {

33     int n,x,y;

34     scanf("%d",&n);

35     while(n--){

36         scanf("%s%s",a,b);

37         x=strlen(a);

38         y=strlen(b);

39         getn(x);

40         printf("%d\n",getnum(x,y));

41     }

42     return 0;

43 }