POJ 3461 kmp
Oulipo
| Time Limit: 1000MS | Memory Limit: 65536K |
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:
[blockquote]
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…
[/blockquote]
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
BAPC 2006 Qualification
莫名其妙TLE
1 #include<iostream>
2 #include<cstdio>
3 #include<cstring>
4 using namespace std;
5 char a[10001];
6 char b[1000001];
7 int p[10001];
8 int la,lb;
9 int j;
10 int ans;
11 inline void makep()
12 {
13
14 j=0;
15 for(int i=1;i<la;i++)
16 {
17 while(j>0&&a[i]!=a[j])
18 j=p[j];
19 if(a[i]==a[j])
20 j++;
21 p[i]=j;
22 }
23 return ;
24 }
25 inline void KMP()
26 {
27 j=0;
28 ans=0;
29 for(int i=0;i<lb;i++)
30 {
31 while(b[i]!=a[j]&&j>0)
32 j=p[j-1];
33 if(b[i]==a[j])
34 j++;
35 if(j==la)
36 {
37 ans++;
38 j=p[j-1];
39 }
40
41 }
42 printf("%d\n",ans);
43 return ;
44 }
45
46 int main()
47 {
48 int n;
49 scanf("%d",&n);
50
51 for(int i=1;i<=n;i++)
52 {
53 memset(p,0,sizeof(p));
54 scanf("%s%s",a,b);
55 la=strlen(a);lb=strlen(b);
56 makep();
57 KMP();
58 }
59
60
61 return 0;
62 } TLEAC
1 #include<cstdio>
2 #include<cstdlib>
3 #include<cstring>
4 #include<iostream>
5 using namespace std;
6
7 int n,la,lb;
8 int next[100010];
9 char a[1000010],b[100010];
10
11 void getnext()
12 {
13 int j=-1;
14 next[0]=-1;
15 for(int i=1;i<lb;i++)
16 {
17 if(j!=-1 && b[j+1]!=b[i]) j=next[j];
18 if(b[j+1]==b[i]) j++;
19 next[i]=j;
20 }
21 }
22
23 int kmp()
24 {
25 int ans=0;
26 int j=-1;
27 for(int i=0;i<la;i++)
28 {
29 if(j!=-1 && a[i]!=b[j+1]) j=next[j];
30 if(b[j+1]==a[i]) j++;
31 if(j==lb-1)
32 {
33 ans++;
34 j=next[j];
35 }
36 }
37 return ans;
38 }
39
40 int main()
41 {
42 scanf("%d",&n);
43 for(int u=1;u<=n;u++)
44 {
45 scanf("%s %s",b,a);
46 la=strlen(a);
47 lb=strlen(b);
48 getnext();
49 printf("%d\n",kmp());
50 }
51 } AC