http://acm.hdu.edu.cn/showproblem.php?pid=1686

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

Source

华东区大学生程序设计邀请赛_热身赛

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#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
const int N = ;
int c[N] ;
int n ;
//int p[220009] ;
char a[] ;
char b[];

void getnext(char *b , int *next)
{
int len = strlen(b);
int j = , k = - ;
next[] = - ;
while(j < len)//查找多次且可重叠时len不能减一，因为该单词的末尾加一的next也需要被下一次查询用到。
{
if(k == - || b[k] == b[j])
{
k++;
j++;
// 下面nest数组的优化
if(b[k] != b[j])
next[j] = k ;
else
next[j] = next[k];
}
else
{
k = next[k];
}
}
}

int main()
{
int n ;
scanf("%d" , &n);
while(n--)
{
int next[];
scanf("%s" , b);
scanf("%s" , a);
int lena = strlen(a) , lenb = strlen(b);
getnext(b, next);
int i = , j = ;
int ans = ;
while(i < lena)
{
if(j == - || a[i] == b[j])
{
i++ ;
j++ ;
}
else
{
j = next[j];
}
if(j == lenb)
{
ans++;
j = next[j] ;
}
}
printf("%d\n" , ans);
}

return  ;  

}