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Ahmed_Negm

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Feb 26th, 2023
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  1. #include <bits/stdc++.h>
  2. #include <ext/pb_ds/assoc_container.hpp>
  3. #include <ext/pb_ds/tree_policy.hpp>
  4. using namespace std;
  5. using namespace __gnu_pbds;
  6. #define ll long long
  7. #define OO 2'000'000'000
  8. #define ull unsigned long long
  9. #define nl '\n'
  10. #define sz(x) (ll)(x.size())
  11. #define all(x) x.begin(),x.end()
  12. #define rall(s)  s.rbegin(), s.rend()
  13. #define getline(s) getline(cin>>ws,s)
  14. #define ceill(n, m) (((n) / (m)) + ((n) % (m) ? 1 : 0))
  15. #define pi  3.141592653589793
  16. #define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
  17. #define multi_ordered_set tree<int, null_type,less_equal<int>, rb_tree_tag,tree_order_statistics_node_update>
  18.  
  19.  
  20. void Fast_IO(){
  21.     ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
  22. // freopen("filename.in", "r", stdin);
  23. // freopen("filename.txt", "w", stdout);
  24. #ifndef ONLINE_JUDGE
  25.     freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
  26. #endif
  27. }
  28.  
  29.  
  30.  
  31.  
  32. int dx[] = { 2, 1, -1, -2, -2, -1, 1, 2 };
  33. int dy[] = { 1, 2, 2, 1, -1, -2, -2, -1 };
  34.  
  35.  
  36.  
  37.  
  38. void solve() {
  39.     ll n;
  40.     cin >> n;
  41.     vector<ll> v(n), reorder(n);
  42.  
  43.     for (auto &i: v) cin >> i;
  44.     if (n == 1) return cout << "YES", void();
  45.     if (n == 2) {
  46.         if (v[0] == v[1]) return cout << "NO", void();
  47.         return cout << "YES", void();
  48.     }
  49.     sort(rall(v));
  50.     for (int i = 0; i < n; i += 2) {
  51.         reorder[i] = v.back();
  52.         v.pop_back();
  53.     }
  54.     for (int i = 1; i < n; i += 2) {
  55.         reorder[i] = v.back();
  56.         v.pop_back();
  57.     }
  58.  
  59.  
  60.     for (int i = 1; i < n - 1; i++) {
  61.         if (i % 2) {
  62.             if (reorder[i] > reorder[i - 1] and reorder[i] > reorder[i + 1]) continue;
  63.             else return cout << "NO", void();
  64.         } else {
  65.             if (reorder[i] < reorder[i - 1] and reorder[i] < reorder[i + 1]) continue;
  66.             else return cout << "NO", void();
  67.         }
  68.     }
  69.     cout << "YES";
  70.  
  71. }
  72.  
  73. int main(){
  74.     Fast_IO();
  75.     int t =1;
  76. //cin>>t;
  77.     while(t--){
  78.         solve();
  79.     }
  80.     return 0;
  81. }
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