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hdoj 1686 Oulipo(kmp)

2024-11-21 10:54:02   202人阅读

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
 
题意：给定一个字符串，求它在另一串出现的次数
 
 1 #include <iostream>
 2 #include <stdio.h>
 3 #include <string.h>
 4 using namespace std;
 5 const int maxn=1e6+10;
 6 int Next[maxn];
 7 char str[maxn],mo[maxn];
 8 void getNext(){
 9     int i=0,j=-1,len=strlen(mo);
10     while(i<len)
11     { if (j==-1||mo[i]==mo[j])
12         Next[++i]=++j;
13         else j=Next[j];
14     }
15 }
16 int kmp(){
17     int i=0,j=0,l1=strlen(str),l2=strlen(mo);
18     int ans=0;
19     while(i<l1)
20     {
21         if(j==-1||mo[j]==str[i])
22             i++,j++;
23         else j=Next[j];
24         if(j==l2)  ans++;
25     }
26     return ans;
27 }
28 int main()
29 {  int t;
30     scanf("%d",&t);
31     while(t--){
32     scanf("%s%s",mo,str);
33     Next[0]=-1;
34      getNext();
35     //for(int i=0;i<strlen(mo);i++)
36     //cout<<Next[i]<<" "; cout<<endl;    查看next数组
37     printf("%d\n",kmp());
38     }
39     return 0;
40 }
41 /*
42 后人修改过后的KMP算法
43  针对aaaaabcde    模式串：aaaaax
44 int j=0,i=1;
45 next[1]=0;
46 while(i<t[0])  // t[0]存放模式串大小
47 {
48     if(j==0||T[i]==T[j])
49     {
50         i++;
51         j++；
52         if(T[i]!=T[j])
53             next[i]=j;
54         else next[i]=next[j];
55     }
56     else j=next[j];
57 }
58 */

 

 

hdoj 1686 Oulipo(kmp)


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