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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define pb push_back
  4. #define ll long long
  5.  
  6. int main() {
  7. 	int t;
  8. 	cin>>t;
  9.  
  10.  
  11. 	while(t--)
  12. 	{
  13. 	    int n;
  14. 	    cin>>n;
  15.         ll a[n];
  16.         multiset<ll> s;
  17.  
  18.         for(int i=0;i<n;i++) {cin>>a[i];s.insert(a[i]);}
  19.  
  20.  
  21.         vector<vector<int>> ans(2);
  22.  
  23.         int flag[2];
  24.         flag[0]=1,flag[1]=1;
  25.  
  26.         //flag[0]
  27.         ll e=*s.begin();
  28.         s.erase(s.find(e));
  29.         ans[0].pb(e);
  30.         int b=1;
  31.  
  32.         while(!s.empty() && flag[0]==1)
  33.         {    
  34.              ll val=-1;
  35.              if(b==1) {auto e1=prev(s.end());  if(*e1>e) val=*e1;else {flag[0]=0;continue;}}
  36.              else { auto e1=s.begin(); if(*e1<e) val=*e1;else {flag[0]=0;continue;} }  
  37.  
  38.  
  39.             // cout<<val<<" "<<b<<endl;
  40.             s.erase(s.find(val));
  41.             ans[0].pb(val);
  42.             e=val;
  43.             b=1-b;
  44.         }
  45.  
  46.         s.clear();
  47.         for(int i=0;i<n;i++) s.insert(a[i]);
  48.         e=*s.rbegin();
  49.         s.erase(s.find(e));
  50.         ans[1].pb(e);
  51.         b=0;
  52.  
  53.         while(!s.empty() && flag[1]==1)
  54.         {    
  55.              ll val=-1;
  56.              if(b==1) {auto e1=prev(s.end());  if(*e1>e) val=*e1;else {flag[1]=0;continue;}}
  57.              else { auto e1=s.begin(); if(*e1<e) val=*e1;else {flag[1]=0;continue;} }  
  58.  
  59.  
  60.             // cout<<val<<" "<<b<<endl;
  61.             s.erase(s.find(val));
  62.             ans[1].pb(val);
  63.             e=val;
  64.             b=1-b;
  65.         }
  66.  
  67.  
  68.         if(flag[0]==1) {for(int i=0;i<ans[0].size();i++) cout<<ans[0][i]<<" ";}
  69.         else
  70.         {
  71.             if(flag[1]==1) {for(int i=0;i<ans[1].size();i++) cout<<ans[1][i]<<" ";}
  72.             else cout<<-1;
  73.         }
  74.         cout<<endl;
  75.  
  76.  
  77.  
  78.  
  79.  
  80.  
  81. 	}
  82. 	return 0;
  83. }
  84.  
Success #stdin #stdout 0.01s 5316KB
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https://ideone.com/WzvdMT
language:
C++14 (gcc 8.3)
created:
1 year ago
visibility:
secret

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