Submission #632197

#	Time	Username	Problem	Language	Result	Execution time	Memory
632197		Minindu2006	Thousands Islands (IOI22_islands)	C++17	6.75 / 100	35 ms	7344 KiB

islands

#include "islands.h"
#include<bits/stdc++.h>
#include <variant>
#include <vector>
using namespace std;
int n, m, can = -1;
vector<int> u, v, vis;
vector<pair<int, int>> adj[1001];
void dfs(int node, vector<int> &ans)
{
  vis[node] = 1;
  if(node == 0)
  {
    if(adj[node].size() >= 2)
    {
      can = 1;
      vector<int> cur(4);
      for(int i=0;i<2;i++)
      {
        int bNum = adj[node][i].second;
        cur[2 * i] = bNum;
        cur[2 * i + 1] = (bNum % 2 == 1 ? bNum - 1:bNum + 1);
        ans.push_back(cur[2 * i]);
        ans.push_back(cur[2 * i + 1]);
      }
      ans.push_back(cur[1]);
      ans.push_back(cur[0]);
      ans.push_back(cur[3]);
      ans.push_back(cur[2]);
      return;
    }
  }
  else
  {
    if(adj[node].size() >= 3)
    {
      can = 1;
      int i = 0, lboat1 = ans.back(), lboat2 = (lboat1 % 2 == 1 ? lboat1 - 1:lboat1 + 1), sz = ans.size();;
      vector<int> cur(4);
      for(auto k:adj[node])
      {
        if(i == 2)
          break;
        if(k.second == lboat2)
          continue;
        int bNum = k.second;
        cur[2 * i] = bNum;
        cur[2 * i + 1] = (bNum % 2 == 1 ? bNum - 1:bNum + 1);
        ans.push_back(cur[2 * i]);
        ans.push_back(cur[2 * i + 1]);
        i++;
      }
      ans.push_back(cur[1]);
      ans.push_back(cur[0]);
      ans.push_back(cur[3]);
      ans.push_back(cur[2]);
      for(int i=sz-1;i>=0;i--)
        ans.push_back(ans[i]);
      return;
    }
  }
  for(auto a:adj[node])
  {
    if(vis[a.first])
      continue;
    ans.push_back(a.second);
    dfs(a.first, ans);
    if(can == 1)
      return;
    ans.pop_back();
  }
}

std::variant<bool, std::vector<int>> find_journey(int N, int M, std::vector<int> U, std::vector<int> V) {
  n = N, m = M;
  u = U, v = V;
  
  vector<int> ans;
  if(n <= 2)
  {
    if(m <= 2)
      return false;
    int z = 0;
    vector<int> cur(3);
    for(int i=0;i<m;i++)
    {
      if(u[i] == 0)
      {
        if(z < 2)
          cur[z] = i;
        z++;
      }
      else
        cur[2] = i;
    }
    if(z < 2 || z == m)
      return false;
    ans.resize(3);
    ans[0] = cur[0];
    ans[1] = cur[2];
    ans[2] = cur[1];
    for(int i=0;i<3;i++)
      ans.push_back(ans[i]);
    return ans;
  }
  vis.resize(n, 0);
  for(int i=0;i<m;i+=2)
  {
    adj[u[i]].push_back({v[i], i});
    adj[v[i]].push_back({u[i], i + 1});
  }
  dfs(0, ans);
  if(can)
    return ans;
  return false;
}

• Subtask 1: 5 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 0 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45