Submission #315280

#	Time	Username	Problem	Language	Result	Execution time	Memory
315280		casperwang	Cat (info1cup19_cat)	C++14	100 / 100	546 ms	20200 KiB

cat

#include <bits/stdc++.h>
#define int long long
#define pb push_back
#define pii pair<int,int>
#define ff first
#define ss second
using namespace std;
 
const int MAXN = 3000000;
int t, n;
int a[MAXN+1];
int c[MAXN+1];
int p[MAXN+1];
bool need[MAXN+1];
int tmp[MAXN+1];
int cnt;
vector <pii> ans;

void swp(int x, int y) {
  swap(a[n-x+1], a[n-y+1]);
  swap(p[a[n-x+1]], p[a[n-y+1]]);
  swap(a[x], a[y]);
  swap(p[a[x]], p[a[y]]);
}

void solve(int N) {
  for (int i = 1; i <= N; i++) {
    if (need[i]) {
      int t = p[i];
      while (!need[t] && t != i) t = p[t];
      if (t == i) continue;
      ans.pb(pii(i, n-t+1));
      swp(i, t);
      need[i] = need[t] = 0;
    }
  }
  for (int i = 1; i <= N; i++) {
    if (a[i] != i) {
      swap(need[i], need[p[i]]);
      ans.pb(pii(i, p[i]));
      swp(i, p[i]);
    }
  }
  cnt = 0;
  for (int i = 1; i <= N; i++) {
    if (need[i]) {
      if (cnt % 2) {
        ans.pb(pii(i, tmp[0]));
        ans.pb(pii(i, n-tmp[0]+1));
        need[i] = need[n-tmp[0]+1] = 0;
      }
      cnt++;
      tmp[0] = n-i+1;
    }
  }
}

signed main() {
  ios_base::sync_with_stdio(0), cin.tie(0);
  cin >> t;
  while (t--) {
    cin >> n;
    bool tf = 1;
    for (int i = 1; i <= n; i++) {
      cin >> a[i];
      p[a[i]] = i;
      need[i] = 0;
      c[i] = tmp[i] = 0;
    }
    ans.clear();
    cnt = 0;
    for (int i = 1; i <= n/2 && tf; i++) {
      if (abs(a[n-i+1] + a[i]) != n+1) tf = 0;
      if (a[i] > n/2) {
        swap(a[n-i+1], a[i]);
        swap(p[a[i]], p[a[n-i+1]]);
        need[i] = 1;
        cnt++;
      }
    }
    if (cnt % 2) tf = 0;
    if (!tf) {
      cout << -1 << "\n";
    } else {
      solve(n/2);
      cout << ans.size() << " " << ans.size() << "\n";
      for (pii o : ans)
        cout << o.ff << " " << o.ss << "\n";
    }
  }
}

• Subtask 1: 15 / 15
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 15 / 15
• Subtask 5: 35 / 35