[HDU](1686)Oulipo ---KMP（串）

Oulipo

Problem 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

 

题意：给你一个模式串和文本串，问你模式串在文本串中出现了几次。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int nex[1000005];
void setNext(char *s2)
{
    int t=-1;
    nex[0]=-1;
    int j=0;
    int s2len=strlen(s2);
    while(j<s2len)
    {
        if(t<0 || s2[j]==s2[t])
        {
            j++;
            t++;
            nex[j]=t;
        }
        else
            t=nex[t];
    }
}
int kmp(char *s1,char *s2)
{
    setNext(s2);
    int s1len=strlen(s1);
    int s2len=strlen(s2);
    int i=0;
    int j=0;
    int flag=0;
    while(i<s1len)
    {
        if(j<0 || s1[i]==s2[j])
        {
            i++;
            j++;
        }
        else
            j=nex[j];
        if(j==s2len)
        {
            flag++;
        }
    }
    return flag;
}
int main()
{
    int t;
    scanf("%d",&t);
    char s2[1000005];
    char s1[1000005];
    while(t--)
    {
        scanf("%s",s2);
        scanf("%s",s1);
        int r=kmp(s1,s2);
        printf("%d\n",r);
    }
    return 0;
}