cf 983A Finite or not?

一 原题

A. Finite or not?
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

You are given several queries. Each query consists of three integers ppqq and bb. You need to answer whether the result of p/qp/q in notation with base bb is a finite fraction.

A fraction in notation with base bb is finite if it contains finite number of numerals after the decimal point. It is also possible that a fraction has zero numerals after the decimal point.

Input

The first line contains a single integer nn (1n1051≤n≤105) — the number of queries.

Next nn lines contain queries, one per line. Each line contains three integers ppqq, and bb (0p10180≤p≤10181q10181≤q≤10182b10182≤b≤1018). All numbers are given in notation with base 1010.

Output

For each question, in a separate line, print Finite if the fraction is finite and Infinite otherwise.

Examples
input
Copy
2
6 12 10
4 3 10
output
Copy
Finite
Infinite
input
Copy
4
1 1 2
9 36 2
4 12 3
3 5 4
output
Copy
Finite
Finite
Finite
Infinite
Note

612=12=0,510612=12=0,510

43=1,(3)1043=1,(3)10

936=14=0,012936=14=0,012

412=13=0,13


二 分析

题意是说给你三个数p,q,b.问你分数p/q在b进制下是否是有穷小数。首先把q除去p,q的最大公约数得到新的q.p/q是有穷小数等价于新的q的素因子都是b的素因子。因为p,q,b最大都是max=10^18,直接分解素因子需要sqrt(max)次操作,会超时。我在比赛的时候想到的办法是求q和b的最大公约数t,只要分解q/t和t中较小的一个就可以了,复杂度就变成了两次开根。更多人选择的解法见下面代码,话说c++17已经自带了std::gcd函数,在头文件<numeric>里。

三 代码

#include <cstdio>
#include <numeric>

typedef long long LL;

using std::gcd;

int n;
LL p, q, b;

int main() {
	scanf("%d", &n);
	while (n--) {
		scanf("%lld%lld%lld", &p, &q, &b);
		q /= gcd(p, q);
		while (true) {
			LL g = gcd(q, b);
			if (g == 1) break;
			while (q % g == 0) q /= g;
		}
		if (q == 1) puts("Finite");
		else puts("Infinite");
	}
	return 0;
}

F. Attraction Theory time limit per test2 seconds memory limit per test256 megabytes Taylor Swift - Love Story (Taylor's Version) ⠀ There are 𝑛 people in positions 𝑝1,𝑝2,…,𝑝𝑛 on a one-dimensional coordinate axis. Initially, 𝑝𝑖=𝑖 for each 1≤𝑖≤𝑛. You can introduce an attraction at some integer coordinate 𝑥 (1≤𝑥≤𝑛), and then all the people will move closer to the attraction to look at it. Formally, if you put an attraction in position 𝑥 (1≤𝑥≤𝑛), the following changes happen for each person 𝑖 (1≤𝑖≤𝑛): if 𝑝𝑖=𝑥, no change; if 𝑝𝑖<𝑥, the person moves in the positive direction, and 𝑝𝑖 is incremented by 1; if 𝑝𝑖>𝑥, the person moves in the negative direction, and 𝑝𝑖 is decremented by 1. You can put attractions any finite number of times, and in any order you want. It can be proven that all positions of a person always stays within the range [1,𝑛], i.e. 1≤𝑝𝑖≤𝑛 at all times. Each position 𝑥 (1≤𝑥≤𝑛), has a value 𝑎𝑥 associated with it. The score of a position array [𝑝1,𝑝2,…,𝑝𝑛], denoted by 𝑠𝑐𝑜𝑟𝑒(𝑝), is ∑𝑛𝑖=1𝑎𝑝𝑖, i.e. your score increases by 𝑎𝑥 for every person standing at 𝑥 in the end. Over all possible distinct position arrays 𝑝 that are possible with placing attractions, find the sum of 𝑠𝑐𝑜𝑟𝑒(𝑝). Since the answer may be large, print it modulo 998244353. Input Each test contains multiple test cases. The first line contains the number of test cases 𝑡 (1≤𝑡≤104). The description of the test cases follows. The first line of each test case contains a single integer 𝑛 (1≤𝑛≤2⋅105). The second line of each test case contains 𝑛 integers — 𝑎1,𝑎2,…,𝑎𝑛 (1≤𝑎𝑖≤109) It is guaranteed that the sum of 𝑛 over all test cases does not exceed 2⋅105. Output For each test case, output a single line containing an integer: the sum of 𝑠𝑐𝑜𝑟𝑒(𝑝) over all possible distinct position arrays 𝑝 that are possible with placing attractions, modulo 998244353. Example inputCopy 7 1 1 2 5 10 3 1 1 1 4 1 1 1 1 4 10 2 9 7 5 1000000000 1000000000 1000000000 1000000000 1000000000 8 100 2 34 59 34 27 5 6 outputCopy 1 45 24 72 480 333572930 69365 Note In the first test case, the only possible result is that person 1 stays at 1. The score of that is 𝑎1=1. In the second test case, the following position arrays [𝑝1,𝑝2] are possible: [1,2], score 15; [1,1], score 10; [2,2], score 20. The sum of scores is 15+10+20=45. In the third test case, the following position arrays [𝑝1,𝑝2,𝑝3] are possible: [1,1,1]; [1,1,2]; [1,2,2]; [1,2,3]; [2,2,2]; [2,2,3]; [2,3,3]; [3,3,3]. Each has a score of 3, and thus the total sum is 24.解决这道题,用c++
09-25
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