PapaMelon #11¼ÆËãÅÅÁеıàºÅ [×éºÏÊýѧ]

#include <iostream>
#include <vector>

using namespace std;

using ll = long long;

vector<ll> f(21);
void init() {
  f[0] = 1;
  for (int i = 1; i <= 20; i++) f[i] = f[i - 1] * i;
}

int main(int argc, char const* argv[]) {
  init();

  int T;
  cin >> T;
  while (T--) {
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    vector<int> vis(n + 1, false);

    ll skip = 0;
    for (int i = 0; i < n; i++) {
      int count = 0;
      for (int k = 1; k < a[i]; k++)
        if (!vis[k]) count++;
      skip += count * f[n - i - 1];
      vis[a[i]] = true;
    }
    cout << skip + 1 << endl;
  }

  return 0;
}