HDU 1686 - Oulipo - [KMP模板题]

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

Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)

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

题目大意：给出一个模式串和一个文本串，求文本串中模式串出现了几次。

解题思路：直接使用KMP算法。

 #include<cstdio>
 #include<cstring>
 #include<iostream>
 #define MAXpat 10000+5
 #define MAXstr 1000000+5
 using namespace std;
 int Next[MAXpat];
 char str[MAXstr],pat[MAXpat];
 
 void getNext()
 {
     int i=, j=-, len=strlen(pat);
     Next[]=-;
     while(i<len)
     {
         if(j == - || pat[i] == pat[j]) Next[++i]=++j;
         else j=Next[j];
     }
 }
 int kmp()
 {
     int i=, j=, len1=strlen(str), len2=strlen(pat);
     int ans=;
     while(i<len1)
     {
         if(j == - || str[i] == pat[j]) i++, j++;
         else j=Next[j];
         if(j == len2) ans++;
     }
     return ans;
 }
 
 int main()
 {
     int t;
     scanf("%d",&t);
     while(t--)
     {
         scanf("%s%s",pat,str);
         getNext();
         printf("%d\n",kmp());
     }
 }