HDU-1686 Oulipo

学习：重点理解这句话的意思： next[j]会告诉我们从哪里开始匹配     模板题。    

                    Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 3612    Accepted Submission(s): 1428

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

华东区大学生程序设计邀请赛_热身赛

 

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#include"stdio.h"
#include"string.h"
int next[10001],num;
char a[1000001],b[10001];
int lena,lenb;
void  get_next()
{
 int i,j;
 i=0;next[0]=-1;j=-1;
 while(i<lenb)
 {
  if(j==-1||b[i]==b[j])
  {
   i++;
   j++;
   if(b[i]==b[j])
   {
    next[i]=next[j];
   }
   else
   {
    next[i]=j;
   }
  }
  else
  {
   j=next[j];
  }
 }
}
void kmp()
{
 int i,j;
  i=0;
  j=0;
  num=0;
 while(i<lena)
 {
  if(a[i]==b[j]||j==-1)
  {
   i++;
   j++;
  }
  else
  {
   j=next[j];
  }
  if(j==lenb)//当j==Lenb next[j]会告诉我们从哪里开始匹配
  {
     num++;
     j=next[j];
  }
 }
 printf("%d\n",num);
}
int main()
{
 int n;
 while(scanf("%d",&n)!=EOF)
 {
       getchar();
  while(n--)
  {
     gets(b);
     gets(a);
     lena=strlen(a);
     lenb=strlen(b);
      get_next();
     kmp();
  }
 }
 return 0;
}