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
BAPC 2006 Qualification
题目大意是这样的： 跟你多组数据， 每组数据中包含两个字符串W和T，询问W在T中出现了多少次。
显然要用KMP
#include <iostream> #include <cstdio> #include <cstring> using namespace std; const int SZ = 10010; const int LA = 1000010; int nxt[SZ]; void getnxt(char n[]) { nxt[0] = nxt[1] = 0; int len = strlen(n); for(int i = 1; i < len; i ++) { int j = nxt[i]; while(j && n[i] != n[j]) j = nxt[j]; nxt[i + 1] = (n[i] == n[j] ? j + 1 : 0); } } int kmp(char n[], char m[]) { int ans = 0; int len1 = strlen(n), len2 = strlen(m); for(int i = 0, j = 0; i < len2; i ++) { while(j && n[j] != m[i]) j = nxt[j]; if(n[j] == m[i]) j ++; if(j == len1) ans ++; } return ans; } int main() { int t; scanf("%d", &t); while(t --) { memset(nxt, 0, sizeof(nxt)); char n[SZ], m[LA]; scanf("%s", n); scanf("%s", m); getnxt(n); printf("%d\n", kmp(n, m)); } }转载于:https://www.cnblogs.com/Loi-Vampire/p/6017057.html
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