POJ3461 Qulipo(kmp)

传送门

 

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 24124		Accepted: 9679

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

 

裸字符串匹配，KMP算法

#include<set>
#include<queue>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int N = 1000010;
#define For(i,n) for(int i=1;i<=n;i++)
#define Rep(i,l,r) for(int i=l;i<=r;i++)
char s1[N],s2[N];
int n,T,m,next[N];

void BuildNext(){
    int pre=0;n=strlen(s1+1),m=strlen(s2+1);
    Rep(i,2,n){
        while(pre&&s1[pre+1]!=s1[i]) pre=next[pre];
        if(s1[pre+1]==s1[i]) pre++;
        next[i]=pre;
    }
}

void KMP(){
    int is1=0,ans=0;
    For(is2,m){
        while(is1&&s1[is1+1]!=s2[is2]) is1=next[is1];
        if(s1[is1+1]==s2[is2]) is1++;
        if(is1==n){
            ans++;
            is1=next[is1];
        }
    }
    printf("%d
",ans);
}

int main(){
    scanf("%d",&T);
    For(i,T){
        scanf("%s%s",s1+1,s2+1);
        BuildNext();
        KMP();
    }
    return 0;
}