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Oulipo

Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 26367 Accepted: 10522

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

计算字串在母串中出现的次数

#include<stdio.h>
#include<iostream>
#include<math.h>
#include<stdlib.h>
#include<ctype.h>
#include<algorithm>
#include<vector>
#include<string.h>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<sstream>
#include<time.h>
#include<malloc.h>

using namespace std;

char a[100000500], b[10005000];
int Next[10005000],ans;

void get_next(char b[], int m)
{
    int i = 0;
    Next[0] = -1;
    int j = -1;
    while (i<m)
    {
        if (j == -1 || b[i] == b[j])
        {
            ++i;
            ++j;
            if (b[i] == b[j])
                Next[i] = Next[j];
            else
                Next[i] = j;
        }
        else
            j = Next[j];
    }
}
int KMP(char a[], int n, char b[], int m, int Next[], int pos)
{
    int i = pos;
    int j = 0;
    while (i<n&&j<m)
    {
        if (j == -1 || a[i] == b[j])
        {
            ++i;
            ++j;
        }
        else
            j = Next[j];
        if (j == m)
        {
            ans++;
            j = Next[j];
        }
    }
    return ans;

}
int main()
{
    int test, n, m, i, j;
    scanf("%d", &test);
    while (test--)
    {
        scanf("%s%s",a,b);
        int n = strlen(a);
        int m = strlen(b);
        get_next(a, n);
        ans = 0;
        KMP(b, m, a, n, Next, 0);
        printf("%d\n",ans);
    }
}