HDU 1686 Oulipo（优化的KMP）

Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 17441    Accepted Submission(s):
6938

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

 #include <iostream>
 #include<cstdio>
 #include<string>
 #include<cstring>
 int next[], num;
 char a[], b[];
 int lena, lenb;
 void  get_next()//自身和自身比较，找某种特征
 {
     int i, j;
     i = ; next[] = -; j = -;
     while (i<lenb)
     {
         if (j == - || b[i] == b[j])//匹配成功的话，继续下一位
         {
             i++;
             j++;
             if (b[i] == b[j])
             {
                 next[i] = next[j];
             }
             else
             {
                 next[i] = j;
             }
         }
         else//否则返回到可以匹配的位置
         {
             j = next[j];
         }
     }
 }
 void index_KMP()
 {
     int i, j;
     i = ;
     j = ;
     num = ;
     while (i<lena)
     {
         if (a[i] == b[j] || j == -) //进行两个字符串的匹配
         {
             i++;//匹配成功，往后继续匹配
             j++;
         }
         else//匹配完成一次，代表出现了一次，记录下来
         {
             j = next[j];
         }
         if (j == lenb)//匹配失败，寻找数组中可以匹配的位置
         {
             num++;
             j = next[j];
         }
     }
     printf("%d\n", num);
 }
 int main()
 {
     int n;
     while (scanf("%d", &n) != EOF)
     {
         getchar();
         while (n--)
         {
             gets(b);
             gets(a);
             lena = strlen(a);
             lenb = strlen(b);
             get_next();
             index_KMP();
         }
     }
     return ;
 }