POJ 3461 Oulipo
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http://poj.org/problem?id=3461
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
代码:
#include <iostream> #include <stdio.h> #include <string.h> #include <math.h> #include <cstdio> #include <algorithm> using namespace std; const int maxn = 1e7 + 5; int TT; int nx[maxn]; char S[maxn], T[maxn]; int slen, tlen; void getNext() { int j, k; j = 0, k = -1, nx[0] = -1; while(j < tlen) { if(k == -1 || T[j] == T[k]) nx[++ j] = ++ k; else k = nx[k]; } } int KMP_Count() { int ans = 0; int i = 0, j = 0; if(slen == 1 && tlen == 1) { if(S[0] == T[0]) return 1; else return 0; } getNext(); for(int i = 0; i < slen; i ++) { while(j > 0 && S[i] != T[j]) j = nx[j]; if(S[i] == T[j]) j ++; if(j == tlen) { ans ++; j = nx[j]; } } return ans; } int main() { scanf("%d", &TT); while(TT --) { scanf("%s%s", T, S); slen = strlen(S); tlen = strlen(T); printf("%d\n", KMP_Count()); } return 0; }
KMP 模板 求模式串在主串中出现的次数
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