[POJ] 3461 Oulipo [KMP算法]

Oulipo
Time Limit: 1000MS   Memory Limit: 65536K
Total Submissions: 23667   Accepted: 9492

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

 
 
题解: 统计W串在T串中出现的次数。根据数据规模,KMP算法可AC。
 
代码:
 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<math.h>
 4 #include<ctype.h>
 5 #include<stdlib.h>
 6 #include<stdbool.h>
 7 
 8 #define rep(i,a,b)      for(i=(a);i<=(b);i++)
 9 #define clr(x,y)        memset(x,y,sizeof(x))
10 #define sqr(x)          (x*x)
11 #define LL              long long
12 
13 int i,j,n,num,
14     f[1000003];
15 
16 char p[10003],t[1000003];
17 
18 int init()
19 {
20     clr(p,'\0');
21     clr(t,'\0');
22     clr(f,0);
23     num=0;
24     
25     scanf("%s",p);
26     scanf("%s",t);
27     
28     return 0;
29 }
30 
31 void kmp(char *t, char *p, int *f)
32 {
33     int n,m,j;
34     n = strlen(t); m = strlen(p);
35     getFail(p,f);
36     
37     j = 0;
38     
39     for(i = 0;i < n;i++) {
40         while(j && p[j] != t[i]) j=f[j];
41         if(p[j] == t[i]) j++;
42         if(j == m) num++;
43     }
44 
45     
46 }
47 
48 void getFail(char p[],int f[])
49 {
50     int m,j,i;
51     m = strlen(p);
52     f[0] = 0;f[1] = 0;
53 
54     for(i = 1;i < m;i++) {
55         j = f[i];
56         while(j && p[i] != p[j]) j = f[j];
57         f[i+1]=p[i]==p[j] ? j+1 : 0;
58     }
59 }
60 
61 int main()
62 {
63     int T;
64     scanf("%d",&T);
65     
66     while(T--) {
67         init();
68         getFail(p,f);
69         kmp(t,p,f);
70         printf("%d\n",num);
71     }
72     return 0;
73 }

 

posted @ 2014-08-19 10:12  SXISZERO  阅读(209)  评论(0编辑  收藏  举报