KMP算法之Oulipo

Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 8137    Accepted Submission(s): 3280

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

 

首先，这道题属于一道KMP算法， 只是将此算法逆着用了一下， 求子串在母串中出现的次数。定义一个count记录次数，然后 利用平常的算法就OK。 若子串没在母串中出现过，

最后的count就还等于0啦！

#include<stdio.h>
#include<string.h>

const int MAXN = 1e6+1;

char Mum[MAXN], Son[10001];
int next[MAXN];
int count;
void GetNext(int l2)
{
int i = 0, j = -1;
next[0] = -1;
while(i < l2)
{
if(j == -1 || Son[i]==Son[j])
next[++i] = ++j;
else
j = next[j];
}
}
void KMP(int l1, int l2)
{
int i=0, j=0;
GetNext(l2);
while(i < l1)
{
if(j==-1 || (Mum[i]==Son[j]&&i<l1&&j<l2) )
i++, j++;
else
j = next[j];
if(j == l2)
{
count++;
j = next[j];
}
}
}

int main()
{
int T;

scanf("%d", &T);

while(T--)
{
int Mn, Sn;
scanf("%s", Son);
scanf(" %s", Mum);
Sn = strlen(Son);
Mn = strlen(Mum);
count = 0;
KMP(Mn, Sn);
printf("%d\n", count);
}
return 0;
}