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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. #define pb push_back
  5. #define fi first
  6. #define se second
  7. #define mp make_pair
  8. #define endl '\n';
  9. #define sz(x) ((int)(x).size())
  10. #define min(a, b) a < b ? a : b
  11. #define all(x) (x).begin(), (x).end()
  12. #define rall(x) (x).rbegin(), (x).rend()
  13. #define show(x) cout << #x << " = " << x << endl
  14. #define yes cout << "YES\n"
  15. #define no cout << "NO\n"
  16. void dbg_out()
  17. {
  18.     cerr << endl;
  19. }
  20. template <typename Head, typename... Tail>
  21. void dbg_out(Head H, Tail... T)
  22. {
  23.     cerr << ' ' << H;
  24.     dbg_out(T...);
  25. }
  26. #define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
  27. typedef long long ll;
  28. // const int N = 2e5 + 5;
  29. const int MOD = (1e9) + 7;
  30.  
  31.  
  32. void solve() {
  33.     int N;
  34.     cin >> N;
  35.     int size = 2*N;
  36.     vector<int> slots(size, 0);
  37.     bool possible = true;
  38.     for(int i = N; i >=1; --i){
  39.         bool placed = false;
  40.         for(int p =0; p +i < size; ++p){
  41.             if(slots[p]==0 && slots[p+i]==0){
  42.                 slots[p] = i;
  43.                 slots[p+i] = i;
  44.                 placed = true;
  45.                 break;
  46.             }
  47.         }
  48.         if(!placed){
  49.             possible = false;
  50.             break;
  51.         }
  52.     }
  53.     if(possible){
  54.         string output;
  55.         for(int idx =0; idx < size; ++idx){
  56.             output += to_string(slots[idx]);
  57.             if(idx != size-1){
  58.                 output += ' ';
  59.             }
  60.         }
  61.         cout << output << '\n';
  62.     }
  63.     else{
  64.         cout << "-1\n";
  65.     }
  66. }
  67.  
  68.  
  69.  
  70. int main()
  71. {
  72.     // freopen("input.txt", "r", stdin);
  73.     ios::sync_with_stdio(0);
  74.     cin.tie(0);
  75.     cout.tie(0);
  76.     int T = 1;
  77.     cin >> T;
  78.     while (T--)
  79.     {
  80.         solve();
  81.     }
  82.  
  83.     return 0;
  84. }
  85.  
Success #stdin #stdout 0.01s 5280KB
comments (?)
stdin
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2
13
12
stdout
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13 11 12 8 5 10 2 9 2 5 7 8 11 13 12 10 9 7 6 4 1 1 3 4 6 3
12 10 11 7 5 9 2 8 2 5 7 10 12 11 9 8 6 4 1 1 3 4 6 3
https://ideone.com/2AQKn6
language:
C++14 (gcc 8.3)
created:
5 days ago
visibility:
public

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