Today Pari and Arya are playing a game called Remainders.
Pari chooses two positive integer x and k, and tells Arya k but not x. Arya have to find the value . There are n ancient numbers c1, c2, ..., cn and Pari has to tell Arya if Arya wants. Given k and the ancient values, tell us if Arya has a winning strategy independent of value of x or not. Formally, is it true that Arya can understand the value for any positive integer x?
Note, that means the remainder of x after dividing it by y.
The first line of the input contains two integers n and k (1 ≤ n, k ≤ 1 000 000) — the number of ancient integers and value k that is chosen by Pari.
The second line contains n integers c1, c2, ..., cn (1 ≤ ci ≤ 1 000 000).
Print "Yes" (without quotes) if Arya has a winning strategy independent of value of x, or "No" (without quotes) otherwise.
4 5 2 3 5 12
Yes
2 7 2 3
No
In the first sample, Arya can understand because 5 is one of the ancient numbers.
In the second sample, Arya can't be sure what is. For example 1 and 7 have the same remainders after dividing by 2 and 3, but they differ in remainders after dividing by 7.
题意:给定k和n,给出n个ci,表示你可以知道x%ci。问能否唯一确定x
思路:首先,根据剩余定理,如果我们想知道x%m等于多少,当且仅当我们知道x%m1,x%m2..x%mr分别等于多少,其中m1m2...mr=m,并且mi相互互质,即构成独立剩余系。令m的素数分解为m=p1^k1p2^k2...pr^kr,如果任意i,都有pi^ki的倍数出现在集合中,那么m就能被猜出来。即k是否存在于素数集合或者存在k的整数倍。
#include <bits/stdc++.h> using namespace std; long long gcd(long long a,long long b){ if(b == 0) return a; return gcd(b,a%b); } long long lcm(long long a,long long b){ return a*b/gcd(a,b); } int main() { int n,k; while(cin>>n>>k){ int ans = 1; int temp; for(int i = 1;i <= n;i ++){ scanf("%d",&temp); ans = gcd(k,lcm(ans,temp)); } if(ans == k) cout<<"Yes"<<endl; else cout<<"No"<<endl; } return 0; }