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！

 1 #include<stdio.h>
 2 #include<string.h>
 3
 4 const int MAXN = 1e6+1;
 5
 6 char Mum[MAXN], Son[10001];
 7 int next[MAXN];
 8 int count;
 9 void GetNext(int l2)
10 {
11 int i = 0, j = -1;
12 next[0] = -1;
13 while(i < l2)
14 {
15 if(j == -1 || Son[i]==Son[j])
16 next[++i] = ++j;
17 else
18 j = next[j];
19 }
20 }
21 void KMP(int l1, int l2)
22 {
23 int i=0, j=0;
24 GetNext(l2);
25 while(i < l1)
26 {
27 if(j==-1 || (Mum[i]==Son[j]&&i<l1&&j<l2) )
28 i++, j++;
29 else
30 j = next[j];
31 if(j == l2)
32 {
33 count++;
34 j = next[j];
35 }
36 }
37 }
38
39 int main()
40 {
41 int T;
42
43 scanf("%d", &T);
44
45 while(T--)
46 {
47 int Mn, Sn;
48 scanf("%s", Son);
49 scanf(" %s", Mum);
50 Sn = strlen(Son);
51 Mn = strlen(Mum);
52 count = 0;
53 KMP(Mn, Sn);
54 printf("%d\n", count);
55 }
56 return 0;
57 }