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| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 35732 | Accepted: 14439 |
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:
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
题目链接：http://poj.org/problem?id=3461
题意：求第一个字符串在第二个字符串中出现的次数
很简单的kmp
1 #include <iostream> 2 #include <cstdlib> 3 #include <string> 4 #include <cstring> 5 using namespace std; 6 char w[10010],t[1000010]; 7 int Next[10010]; 8 void get_next() 9 { 10 int i; 11 int j; 12 Next[0] = -1; 13 for(i = 0, j = -1; w[i];) 14 { 15 if(j == -1 || w[i] == w[j]) 16 { 17 i++; 18 j++; 19 if(w[i] != w[j]) 20 Next[i] = j; 21 else 22 Next[i] = Next[j]; 23 } 24 else 25 j = Next[j]; 26 } 27 } 28 int kmp() 29 { 30 int i = 0; 31 int j = 0; 32 int len = strlen(w); 33 int len2 = strlen(t); 34 int ans = 0; 35 while(i < len2 && j < len) 36 { 37 if(j == -1 || t[i] == w[j]) 38 { 39 i++; 40 j++; 41 } 42 else 43 j = Next[j]; 44 if(j >= len) 45 { 46 ans++; 47 j = Next[j]; 48 } 49 } 50 return ans; 51 } 52 int main() 53 { 54 int T; 55 cin >> T; 56 while(T--) 57 { 58 int cnt = 0; 59 cin >> w; 60 cin >> t; 61 get_next(); 62 int ans = kmp(); 63 cout << ans << endl; 64 } 65 return 0; 66 }
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原文地址：http://www.cnblogs.com/Mino521/p/5758154.html
