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[10005];
char s[1000005];
int next[10005];
int lenp,lens;

void getnext()
{
    next[0]=-1;
    int j=-1;
    for (int i=1;i<lenp;i++)
    {
        while (j>-1 && p[j+1]!=p[i]) j=next[j];
        if (p[j+1]==p[i]) j++;
        next[i]=j;
    }
}
int kmp()
{
    int j=-1,count=0;
    for (int i=0;i<lens;i++)
    {
        while (j>-1 && p[j+1]!=s[i]) j=next[j];
        if (p[j+1]==s[i]) j++;
        if (j==lenp-1)
        {
            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
",kmp());
    }
    return true;
}