【POJ3461】Olipo

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

题意：看样例。

KMP模板，程序模拟+手动模拟大概是明白了一些。

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

char A[1000000+10],B[1000000+10];
int T[1000000+10];
int n,ans;

void calc_T()//找到失配函数
{
    T[0]=-1;
    int j,lenA=strlen(A);
    for (int i=0;i<lenA;i++)
    {
        j=T[i];
        while (j!=-1 && A[j]!=A[i])    j=T[j];
        T[i+1]=++j;
    }
}

void kmp(int lenA)
{
    calc_T();
    int j=0,k=0,lenB=strlen(B);
    while (k<lenB && j<lenA)
    {
        if (k==-1 || A[j]==B[k])    j++,k++;
        else    k=T[k];
        if (k==lenB)    ans++,k=T[k];
    }
    //return ans;
}

int main()
{
    while (~scanf("%d",&n))
    {
        for (int i=1;i<=n;i++)
        {
            ans=0;
            scanf("%s%s",B,A);
            kmp(strlen(A));
            printf("%d
",ans);
        }
    }
}