【POJ3461】Oulipo

題面

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

題解

這是一道KMP模闆題

我竟然Wa了N遍才AC（實測N=4）

題目大意：給你T組字元串，問第一個串在第二個中出現了幾次

KMP太毒了，，，，老是寫Wa。。。。

滑稽

這一道題用來複習KMP

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
#define Next nt
char a[],b[];
int nt[];
inline void getnext()//獲得字元串s的next數組
{
    int l=strlen(a),t;
    Next[]=-;//如果在0位置失配則是向下移動一位
    for(int i=;i<l;++i)//依次求解後面的next數組
    {
        t=Next[i-];
        while(a[t+]!=a[i]&&t>=)
            t=Next[t];
        if(a[t+]==a[i])
            Next[i]=t+;
        else
            Next[i]=-;
    }
}
int KMP()
{
       int l=strlen(b);
       int l2=strlen(a); 
       int i=,j=;//比對指針 
       int sum=;
       while(i<l)
       {
               if(a[j]==b[i])
               {
                     j++;i++;
                     if(j==l2)//比對完了
                     {
                            ++sum;
                            j=nt[j-]+;
                     }
               }
               else//失配 
               {
                     if(j==)//首位失配
                           i++;
                     else//跳轉 
                        j=nt[j-]+; 
               }
       }
       return sum;
}
int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        scanf("%s",a);
        scanf("%s",b);
        //memset(nt,0,sizeof(nt));
        getnext();
        cout<<KMP()<<endl;
    }
    return ;

}