Oulipo(KMP)
時間限制: 1 Sec 記憶體限制: 33 MB
題目描述
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.
輸入
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.
輸出
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.
樣例輸入
3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN
樣例輸出
1
3
0
解題思路
KMP演算法,直接套模板。
#include <stdio.h> #include <string.h> char a[1000010], b[10010]; int lena, lenb, next[10010]; void Next() { int i = 0, j = -1; next[0] = -1; while (i < lenb) { if (j == -1 || b[i] == b[j]) { i++; j++; if (b[i] == b[j]) next[i] = next[j]; else next[i] = j; } else j = next[j]; } } void KMP() { int i = 0, j = 0, num = 0; while (i < lena) { if (j == -1 || a[i] == b[j]) { i++; j++; } else j = next[j]; if (j == lenb) { num++; j = next[j]; } } printf("%d\n", num); } int main() { int t; scanf("%d", &t); while (t--) { scanf("%s%s", b, a); lena = strlen(a); lenb = strlen(b); Next(); KMP(); } return 0; }