POJ 3461 Oulipo（KMP裸题）

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

给两个字符串，求第一个字符串在第二个中出现的次数
KMP最精华即next数组
参考博客：http://blog.csdn.net/zz_ylolita/article/details/50650391

 #include<cstdio>
 #include<iostream>
 #include<cstring>
 #include<string.h>
 using namespace std;

 char p[];
 char s[];
 int next[];
 int lenp,lens;

 void getnext()
 {
     next[]=-;
     int j=-;
     for (int i=;i<lenp;i++)
     {
         while (j>- && p[j+]!=p[i]) j=next[j];
         if (p[j+]==p[i]) j++;
         next[i]=j;
     }
 }
 int kmp()
 {
     int j=-,count=;
     for (int i=;i<lens;i++)
     {
         while (j>- && p[j+]!=s[i]) j=next[j];
         if (p[j+]==s[i]) j++;
         if (j==lenp-)
         {
             count++;
             j=next[j];
         }
     }
     return count;
 }

 int main()
 {
     int T;
     scanf("%d",&T);
     while(T--)
     {
         cin>>p>>s;
         lenp=strlen(p);
         lens=strlen(s);
         getnext();
         printf("%d\n",kmp());
     }
     return true;
 }