POJ3461Olipo
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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
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 5 using namespace std; 6 7 char A[1000000+10],B[1000000+10]; 8 int T[1000000+10]; 9 int n,ans; 10 11 void calc_T()//找到失配函数 12 { 13 T[0]=-1; 14 int j,lenA=strlen(A); 15 for (int i=0;i<lenA;i++) 16 { 17 j=T[i]; 18 while (j!=-1 && A[j]!=A[i]) j=T[j]; 19 T[i+1]=++j; 20 } 21 } 22 23 void kmp(int lenA) 24 { 25 calc_T(); 26 int j=0,k=0,lenB=strlen(B); 27 while (k<lenB && j<lenA) 28 { 29 if (k==-1 || A[j]==B[k]) j++,k++; 30 else k=T[k]; 31 if (k==lenB) ans++,k=T[k]; 32 } 33 //return ans; 34 } 35 36 int main() 37 { 38 while (~scanf("%d",&n)) 39 { 40 for (int i=1;i<=n;i++) 41 { 42 ans=0; 43 scanf("%s%s",B,A); 44 kmp(strlen(A)); 45 printf("%d\n",ans); 46 } 47 } 48 }
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