hdu 1686 Oulipo（KMP算法）

                                                     Oulipo

http://blog.youkuaiyun.com/yaochunnian/article/details/7059486
Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 5591    Accepted Submission(s): 2237

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
  
  


  
  

   经典的KMP算法；
  
  

   代码（可当模板）：
  
  

   #include<stdio.h>
#include<string.h>
char a[10010];
char b[1000100];
int next[10010];
void setnext(char a[],int next[])
{
	int i,j,k;
	memset(next,0,sizeof(next));
	i=0;j=-1;
	next[0]=-1;
	int n;
	n=strlen(a);
	for(;i<n;)
	{
		if(j==-1||a[i]==a[j])
		{
			j++;
			i++;
			if(a[i]!=a[j])
			{
				next[i]=j;
			}
			else
			next[i]=next[j];
		}
		else
		j=next[j];
	}
}
int kmp(char a[],char b[])
{
	setnext(a,next);
	int i,j;
	i=0,j=0;
	int la,lb;
	int sum=0;
	la=strlen(a);
	lb=strlen(b);
	for(;i<lb;)
	{
		if(j==-1||b[i]==a[j])
		{
			i++;//i对应主字符串（长），
			j++;//j对应模板字符串（短）
		}
		else
		j=next[j];
		if(j==la)
		sum++;
	}
	return sum;
}
int main()
{
	int T;
	scanf("%d",&T);
	getchar();
	while(T--)
	{
		int t;
		gets(a);
		gets(b);
		t=kmp(a,b);
		printf("%d\n",t);
	}
	return 0;
}