HDOJ-1686 Oulipo ---KMP

Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 5588    Accepted Submission(s): 2235


[align=left]Problem Description[/align]
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.

 

[align=left]Input[/align]
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.

 

[align=left]Output[/align]
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.

 

[align=left]Sample Input[/align]

3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

 

[align=left]Sample Output[/align]

1
3
0

 

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
char s[1000010];
char t[10010];
int next[10010];
void get_next()
{
int i=0;
int j=-1;
next[0]=-1;
int len_t=strlen(t);
while(i<len_t)
{
if(j==-1||t[i]==t[j])
{
i++;
j++;
if(t[i]==t[j])
next[i]=next[j];
else
next[i]=j;
}
else
j=next[j];
}
}
int KMP()
{
int i=-1;
int j=-1;
int len_t=strlen(t);
int len_s=strlen(s);
int count=0;
get_next();
while(i<len_s)
{
if(j==-1||s[i]==t[j])
{
i++;
j++;
}
else
{
j=next[j];
}
if(j==len_t) //优化
{
j=next[j];
count++;
}
}
return count;
}
int main()
{
int T;
scanf("%d",&T);
while(T--)
{
scanf("%s %s",t,s);
printf("%d\n",KMP());
}
return 0;
}