KMP 专场 POJ 3461

Oulipo
Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 24399 Accepted: 9793
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

BAPC 2006 Qualification

<span style="color:#3333ff;">/*********************************
     author   : Grant Yuan
     algorithm; kmp
     source   : POJ 3461
	  time    ；2014/10/3 20:38
 *********************************/   
#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define MAX  400007

using namespace std;
char a[10007];
char b[1000007];
int ans;
int next[10007];
int t,l1,l2;

void get_next()
{
  int i=0,j=-1;
  next[0]=-1;
  for(int i=0;i<l1;)
  {
      if(j==-1||a[j]==a[i])
      {
          i++;j++;
          next[i]=j;
      }
      else j=next[j];
  }
}

int main()
{
    scanf("%d",&t);
    while(t--){
        scanf("%s",a);scanf("%s",b);
        l1=strlen(a);l2=strlen(b);
        get_next();ans=0;
        int i=0,j=0;
         while(i<l2){
           if(a[j]==b[i]){
                i++;
                j++;
            }
            else{
                j=next[j];
                if(j==-1){
                    i++;j=0;
                }
            }
            if(j==l1) ans++;
        }
        printf("%d
",ans);
    }
    return 0;
}
</span>