丑数（摘）

#include<iostream>
#include<queue>
#include<vector>
#include<set>
using namespace std;
typedef long long LL;
const int coeff[3]={2,3,5};
int main() 
{
    priority_queue<LL,vector<LL>,greater<LL> >pq;
    set<LL>s;
    pq.push(1);
    s.insert(1);
    int n;
    cin>>n;
    for(int i=1;;i++){
        LL x=pq.top();
        pq.pop();
        if(i==n){
            cout<<"The "<<n<<"‘th ugly number is "<<x<<".\n";
            break;
        }
        for(int j=0;j<3;j++){
            LL x2=x * coeff[j];
            if(!s.count(x2)){             //计数x2，不为0则存入队列中
                s.insert(x2);
                pq.push(x2);
            }
        }
    }
    system("pause");
    return 0;
}