POJ 3461 - Oulipo（KMP）

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 18241		Accepted: 7323

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

=========================

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

using namespace std;
const int MAXN=1000100;
char w[MAXN],t[MAXN];
int T,ans,f[MAXN];

void getFail(char P[],int f[])
{
int i=0,j=-1;
int len=strlen(P);
f[0]=-1;
while (i<len){
if (j==-1||P[i]==P[j])
{
i++,j++;
f[i]=j;
}
else j=f[j];
}
}

void KMP(char T[],char P[],int f[]){
int i=0,j=0;
int n=strlen(T);
int m=strlen(P);
getFail(P,f);
while(i<n)
{
if(j==-1||T[i]==P[j])
{
i++,j++;
}
else j=f[j];
if(j==m)
{
ans++;
j=f[j];
}
}
}

int main()
{
scanf("%d",&T);
while(T--)
{
ans=0;
scanf("%s%s",w,t);
KMP(t,w,f);
printf("%d\n",ans);
}
return 0;
}