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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. #define int long long
  5.  
  6. int countInversions(const vector<int>& a) {
  7.     int inv = 0;
  8.     int n = a.size();
  9.     for (int i = 0; i < n; ++i)
  10.         for (int j = i+1; j < n; ++j)
  11.             if (a[i] > a[j]) ++inv;
  12.     return inv;
  13. }
  14.  
  15. void solve() {
  16.     int n;
  17.     cin >> n;
  18.     vector<int> p(n);
  19.     for (auto &x : p) cin >> x;
  20.  
  21.     int minInv = LLONG_MAX;
  22.  
  23.     for (int mask = 0; mask < (1 << n); ++mask) {
  24.         vector<int> a(n);
  25.         for (int i = 0; i < n; ++i) {
  26.             if ((mask >> i) & 1)
  27.                 a[i] = 2 * n - p[i];
  28.             else
  29.                 a[i] = p[i];
  30.         }
  31.         int inv = countInversions(a);
  32.         minInv = min(minInv, inv);
  33.     }
  34.  
  35.     cout << minInv << '\n';
  36. }
  37.  
  38. int32_t main() {
  39.     ios::sync_with_stdio(false);
  40.     cin.tie(nullptr);
  41.  
  42.     int t;
  43.     cin >> t;
  44.     while (t--) solve();
  45. }
  46.  
Success #stdin #stdout 0.01s 5320KB
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5
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2 1
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2 1 3
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4 3 2 1
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2 3 1 5 4
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2 3 4 1 5 6
stdout
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0
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https://ideone.com/tF9nW6
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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