kmp
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
1 #include<stdio.h> 2 #include<string.h> 3 #define N 1000005 4 char s[N]; 5 char p[N]; 6 int next[N]; 7 int m,n; 8 void getnext() 9 { 10 int j=0,k=-1; 11 next[0]=-1; 12 while(j<m) 13 { 14 if(k==-1||p[j]==p[k]) 15 { 16 j++; 17 k++; 18 next[j]=k; 19 } 20 else 21 k=next[k]; 22 } 23 } 24 int kmp() 25 { 26 int i=0,j=0,ans=0; 27 getnext(); 28 while(i<n) 29 { 30 if(j==-1||s[i]==p[j]) 31 { 32 i++; 33 j++; 34 } 35 else 36 j=next[j]; 37 if(j==m) 38 ans++; 39 } 40 return ans; 41 } 42 int main() 43 { 44 int t; 45 scanf("%d",&t); 46 while(t--) 47 { 48 scanf(" %s %s",&p,&s); 49 m=strlen(p); 50 n=strlen(s); 51 printf("%d\n",kmp()); 52 } 53 return 0; 54 }
本文来自博客园,作者:左手边五十米,转载请注明原文链接:https://www.cnblogs.com/moomcake/p/8987022.html