POJ 3461 Oulipo

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 38364		Accepted: 15439

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

HASH 版本：

#include<cstdio>
#include<cstring>
using namespace std;
#define P 29
const int N=1e6+10;
char s1[N],s2[N];
int p,ans,S,n1,n2,ha[N];
void get_P(){
    p=1;
    for(int i=1;i<=n2;i++)p*=P;
} 
void get_Hash(){
    ha[0]=0;S=0;
    for(int i=1;i<=n2;i++) S=S*P+s2[i]-'a';
    for(int i=1;i<=n1;i++) ha[i]=ha[i-1]*P+s1[i]-'a';
}
int query(int l,int r){
    return ha[r]-ha[l-1]*p;
}
int main(){
    int T;scanf("%d",&T);
    while(T--){
        ans=0;
        scanf("%s%s",s2+1,s1+1);
        n1=strlen(s1+1);n2=strlen(s2+1);
        get_P();get_Hash();
        for(int i=n2,x;i<=n1;i++){
            x=query(i-n2+1,i);
            if(x==S) ans++;
        }
        printf("%d
",ans);
    }
    return 0;
}

 KMP版本：

#include<cstdio>
#include<cstring>
using namespace std;
const int N=1e6+10;
char s[N],t[N];
int T,n,m,next[N],ans;
void Get_Next(){
    int j=0;
    for(int i=2;i<=m;i++){
        while(j && t[i] != t[j+1])j=next[j];
        if(t[i] == t[j+1])j++;
        next[i]=j;
    }
}
void KMP(){
    int j=0;
    for(int i=1;i<=n;i++){
        while(j && s[i] != t[j+1])j=next[j];
        if(s[i]==t[j+1])j++;
        if(j==m)ans++,j=next[j];
    }
}
int main()
{
    scanf("%d",&T);
    while(T--){
        scanf("%s%s",t+1,s+1);
        ans=0;
        n=strlen(s+1),m=strlen(t+1);
        Get_Next();
        KMP();
        printf("%d
",ans);
    }
    return 0;
}