Submission #1207971

#	Time	Username	Problem	Language	Result	Execution time	Memory
1207971		HappyCapybara	Thousands Islands (IOI22_islands)	C++20	0 / 100	19 ms	6468 KiB

islands

#include "islands.h"
#include<bits/stdc++.h>
using namespace std;

vector<int> u, v;
vector<vector<int>> g;
vector<int> seen, es;
vector<int> p, t, c;

void dfs(int cur){
  if (!c.empty()) return;
  seen[cur] = 1;
  for (int next : g[cur]){
    if (!c.empty()) return;
    if (es[next]) continue;
    es[next] = true;
    int nn = u[next]+v[next]-cur;
    if (seen[nn] == 2) continue;
    if (seen[nn] == 1){
      if (nn == v[next]) c.push_back(next);
      else c.push_back(next+1);
      while (cur != nn){
        if (cur == v[p[cur]]) c.push_back(p[cur]);
        else c.push_back(p[cur]+1);
        cur = u[p[cur]]+v[p[cur]]-cur;
      }
      while (cur != 0){
        if (cur == v[p[cur]]) t.push_back(p[cur]);
        else t.push_back(p[cur]);
        cur = u[p[cur]]+v[p[cur]]-cur;
      }
      reverse(c.begin(), c.end());
      reverse(t.begin(), t.end());
      return;
    }
    if (seen[v[next]] == 0){
      p[v[next]] = next;
      dfs(v[next]);
    }
  }
  seen[cur] = 2;
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V){
  u = U;
  v = V;
  g.resize(N);
  for (int i=0; i<M; i+=2){
    g[U[i]].push_back(i);
    g[V[i]].push_back(i);
  }
  seen.resize(N, 0);
  es.resize(M, 0);
  p.resize(N);
  dfs(0);
  if (c.empty()) return false;
  vector<int> res;
  for (int x : t) res.push_back(x);
  for (int x : c) res.push_back(x);
  reverse(c.begin(), c.end());
  for (int x : c) res.push_back(x^1);
  for (int x : c) res.push_back(x);
  reverse(c.begin(), c.end());
  for (int x : c) res.push_back(x^1);
  reverse(t.begin(), t.end());
  for (int x : t) res.push_back(x);
  return  res;
}

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