【ACM- OJ】《Oulipo》C++

• 题目描述
• 输入
• 输出
• 样例输入
• 样例输出
• AC代码

题目描述

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.

输入

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| ≤ 20,000 (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| ≤ 2,000,000.

输出

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.

样例输入

3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

样例输出

1
3
0

AC代码

//
//  main.cpp
//  Oulipo
//
//  Created by HISS on 2020/11/18.
//

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
#define ull unsigned long long

const int N = 1000005;
const int c = 1331;
char s[N], p[N];
ull ha[N], hp[N];
unsigned long n, m;

void init()
{
    ha[0] = 1;
    for(int i = 1; i <= 1000000; i ++)
        ha[i] = ha[i - 1] * c;
}

int main()
{
    init();
    int t;
    scanf("%d", &t);
    while(t --)
    {
        scanf("%s %s", s, p);
        m = strlen(s);
        n = strlen(p);
        ull x = 0;
        for(int i = 0; i < m; i ++)
            x = x * c + (ull)(s[i] - 'A' + 1);
        hp[0] = (ull)(p[0] - 'A' + 1);
        for(int i = 1; i < n; i ++)
            hp[i] = hp[i - 1] * c + (ull)(p[i] - 'A' + 1);
        int ans = 0;
        if(hp[m - 1] == x)
            ans ++;
        for(int i = 1; i <= n - m; i ++)
            if(hp[i + m - 1] - hp[i - 1] * ha[m] == x)
                ans ++;
        printf("%d\n", ans);
    }
    return 0;
}