Hduoj1686 【KMP】
3438 ワード
/*Oulipo
Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 5501 Accepted Submission(s): 2194
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
_
*/
#include<stdio.h>
#include<string.h>
char s[1000010], ne[10010];
int next[10010], len;
void getnext(int l)// next[len]=
{
next[0] = -1;
int i, j;
i = 0;
j = -1;
while(i < l)
{
if( j == -1 || ne[i] == ne[j])
{
i++;
j++;
if(ne[i]==ne[j])
next[i] = next[j];
else
next[i] = j;
}
else
j = next[j];
}
}
int main()
{
int i ,j, k, m, n;
scanf("%d", &n);
getchar();
while(n--)
{
scanf("%s%s", ne, s);
len = strlen(ne);
k = strlen(s);
getnext(len);
m = 0;
i = -1;
j = -1;
while(i < k)// i text
{
if(j == -1 || s[i] == ne[j])
{
i++;
j++;
}
else
j = next[j];
if(j == len)// ,
m++; // j = next[j]
}
printf("%d
", m);
}
return 0;
}
題意:サブストリングを与え,サブストリングがメインストリングに現れる回数,標準的なkmpアルゴリズムを求める.
難点:kmpのnext配列の具体的な意味を理解するには