1005 继续(3n+1)猜想

#include<cstdio> 
#include<algorithm>
#include<iostream>
#include<vector>
#include<unordered_set>
using namespace std;
main(){
    vector<int>v;
    unordered_set<int>us;
    int n;
    cin>>n;
    int a;
    while(n--){
        cin>>a;
        v.push_back(a);
        while(a!=1){
            if(a%2==1)
            a=a*3+1;
            a/=2;
            us.insert(a);                
        }
    }
    sort(v.begin(),v.end(),greater<int>());
    bool first=true;
    for(auto i:v){
        if(!us.count(i))
        {  cout<<(first?"":" ")<<i;
            first=false;
        }
    }
    return 0;
}