codeforces 962D Merge Equals

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<string>
#include<vector>
#include<map>
#include<queue>
#include<functional>
#define DEBUG(x) cout<<#x<<" = "<<x<<endl
typedef long long ll;
using namespace std;
map<ll,priority_queue<int,vector<int>,greater<int> > >mp;
map<ll,priority_queue<int,vector<int>,greater<int> > >::iterator itr;
vector<pair<int,ll> >v;
bool cmp(const pair<int,ll> &pa,const pair<int,ll> &pb)
{
    return pa.first<pb.first;
}
int main()
{
//    freopen("in.txt","r",stdin);
    int n;
    scanf("%d",&n);
    for(int i=0;i<n ;i++ ){
        ll t;
        scanf("%I64d",&t);
        mp[t].push(i);
    }
    for(itr=mp.begin();itr!=mp.end() ;itr++ ){
        ll t=itr->first;
        auto &pq=itr->second;
        ///合并两个相等的数，直到数量小于2
        while(pq.size()>=2){
            int i1=pq.top();
            pq.pop();
            int i2=pq.top();
            pq.pop();
            i1=max(i1,i2);
            mp[2*t].push(i1);
        }
    }
    for(auto p:mp){
        auto &pq=p.second;
        ll t=p.first;
        if(pq.size()==1)v.push_back(make_pair(pq.top(),t));
    }
    sort(v.begin(),v.end(),cmp);
    printf("%d\n",v.size());
    for(int i=0;i<v.size() ;i++ ){
        printf("%d ",v[i].second);
    }
}