poj 3461 KMP算法求可重复利用的子串个数

这道题想了好久，，提交了好久，，改了好久，，，，，终于ac了，，，，，，学KMP的伤不起啊！！！！！前几天做了不可重复利用的子串的个数，，当时是1A了，本以为这题应该也不难，，，却悲剧了这么久。。。。现在已经不是一天做几道题，，而是几天做一道题，，，，题目：

Oulipo

Time Limit:1000MS		Memory Limit:65536K
Total Submissions:9360		Accepted:3708

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 wordWand a textT, count the number of occurrences ofWinT. All the consecutive characters of W must exactly match consecutive characters ofT. 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 wordW, a string over {'A','B','C', …,'Z'}, with 1 ≤ |W| ≤ 10,000 (here |W| denotes the length of the stringW).
• One line with the textT, 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 wordWin the textT.

Sample Input

3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

Sample Output

1
3
0

ac代码：

#include <iostream>
#include <cstdio>
#include <string.h>
const int N=1000010;
const int M=100010;
int nextt[M],len1,len2;
char str1[N],str2[M];
void get_nextt(){
  int i=0,j=-1;
  nextt[0]=-1;
  while(i<len2){
	  if(j==-1||str2[i]==str2[j]){
	    ++i;++j;
		nextt[i]=j;
	  }
	  else
		  j=nextt[j];
  }
}
int kmp(){
  int count=0,i=0,j=0;
  while(i<len1){
	  if(str1[i]==str2[j]||j==-1){
	    ++i;++j;
	  }
	  else
		  j=nextt[j];
	  if(j==len2){
	    count++;
		j=nextt[j];
	  }
  }
  return count;
}
int main(){
	int numcase;
	scanf("%d",&numcase);
	while(numcase--){
	  scanf("%s%s",str2,str1);
	  len1=strlen(str1);
	  len2=strlen(str2);
	  memset(nextt,0,sizeof(nextt));
	  get_nextt();
	  int x=kmp();
	  printf("%d\n",x);
	}
  return 0;
}