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;
}

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转载自blog.csdn.net/max_kibble/article/details/80339811