Submission #762929

#	Time	Username	Problem	Language	Result	Execution time	Memory
762929		Trunkty	Cat (info1cup19_cat)	C++14	100 / 100	416 ms	20728 KiB

cat

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll

int t;
int n;
int arr[200005],pos[200005];

int val(int x){
    if(x>n/2){
        return n-x+1LL;
    }
    else{
        return x;
    }
}

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> t;
    for(int e=1;e<=t;e++){
        cin >> n;
        for(int i=1;i<=n;i++){
            cin >> arr[i];
        }
        bool bad = false;
        for(int i=1;i<=n/2;i++){
            if(arr[i]+arr[n-i+1LL]!=n+1LL){
                bad = true;
            }
        }
        if(bad){
            cout << -1 << "\n";
            continue;
        }
        for(int i=1;i<=n/2;i++){
            pos[val(arr[i])] = i;
        }
        vector<vector<int>> ans;
        for(int i=1;i<=n/2;i++){
            if(pos[i]!=i){
                if(arr[pos[i]]>n/2){
                    int x = pos[i];
                    arr[x] = n-arr[x]+1LL;
                    arr[i] = n-arr[i]+1LL;
                    swap(arr[i],arr[x]);
                    ans.push_back({i,n-x+1LL});
                    pos[val(arr[i])] = i;
                    pos[val(arr[x])] = x;
                }
                else{
                    int x = pos[i];
                    swap(arr[i],arr[x]);
                    ans.push_back({i,x});
                    pos[val(arr[i])] = i;
                    pos[val(arr[x])] = x;
                }
            }
        }
        int bef=-1;
        for(int i=1;i<=n/2;i++){
            if(arr[i]>n/2){
                if(bef==-1){
                    bef = i;
                }
                else{
                    ans.push_back({bef,i});
                    ans.push_back({bef,n-i+1LL});
                    bef = -1;
                }
            }
        }
        if(bef!=-1){
            cout << -1 << "\n";
        }
        else{
            cout << ans.size() << " " << ans.size() << "\n";
            for(vector<int> i:ans){
                cout << i[0] << " " << i[1] << "\n";
            }
        }
    }
    return 0;
}

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