Submission #864724

#	Time	Username	Problem	Language	Result	Execution time	Memory
864724		mychecksedad	Parking (CEOI22_parking)	C++17	20 / 100	61 ms	16996 KiB

Main

/* Author : Mychecksdead  */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
const int N = 1e6+100, M = 1e5+10, K = 52, MX = 30;


int n, m, A[N], B[N], AA = MOD;
vector<pair<int, int>> ans;
vector<vector<int>> v;
vector<int> E;
array<int, 2> col[N][2];

void move(int i, int j){
  if(i==j) return;
  int x = v[i].back();
  ans.pb({i, j});
  v[j].pb(x);
  v[i].pop_back();
  if(v[i].empty()) E.pb(i);
}

void solve(){
  cin >> n >> m;
  v.resize(m);
  for(int i = 0; i < m; ++i){
    cin >> B[i] >> A[i];
    if(B[i] > 0) v[i].pb(B[i]);
    if(A[i] > 0) v[i].pb(A[i]);
  }
  bool ok = 1;
  for(int i = 0; i < m; ++i) if(v[i].empty()) E.pb(i);
  while(ok){
    ok = 0;
    vector<int> one(n+1, -1), up(n+1, -1);
    for(int i = 0; i < m; ++i){
      if(v[i].empty()) continue;
      else if(v[i].size() == 1){
        if(one[v[i][0]] != -1){
          ok = 1;
          move(i, one[v[i][0]]);
          continue;
        }
        if(up[v[i][0]] != -1){
          ok = 1;
          move(up[v[i][0]], i);
          continue;
        }
        one[v[i][0]] = i;
      }else{
        if(v[i][0] == v[i][1]) continue;
        if(up[v[i][1]] != -1){
          if(!E.empty()){
            int pos = E.back();
            E.pop_back();
            move(up[v[i][1]], pos);
            move(i, pos);
            ok = 1;
          }
          continue;   
        }
        if(one[v[i][1]] != -1){
          ok = 1;
          move(i, one[v[i][1]]);
          continue;
        }
        up[v[i][1]] = i;
      }
    }
    if(ok) continue;
    if(E.empty()) break;
    for(int i = 0; i < m; ++i){
      if(v[i].size() == 2){
        if(v[i][0] == v[i][1]) continue;
        move(i, E.back());
        E.pop_back();
        ok = 1;
        break;
      }
    }
  }
  ok = 1;
  for(int i = 0; i < m; ++i){
    if(v[i].empty()) continue;
    if(v[i].size() == 1) ok = 0;
    else{
      ok &= (v[i][0] == v[i][1]);
    }
  }

  if(!ok){
    cout << -1;
    return;
  }

  cout << ans.size() << '\n';
  for(auto x: ans) cout << x.first + 1 << ' ' << x.second + 1 << '\n';
}


int main(){
  cin.tie(0); ios::sync_with_stdio(0);
  int tt = 1, aa;
  // freopen("in.txt", "r", stdin);
  // freopen("out.txt", "w", stdout);
  while(tt--){
    solve();
  }
  cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
  return 0;
} 

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:108:15: warning: unused variable 'aa' [-Wunused-variable]
  108 |   int tt = 1, aa;
      |               ^~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 15
• Subtask 5: 0 / 25
• Subtask 6: 0 / 15