Submission #631972

#	Time	Username	Problem	Language	Result	Execution time	Memory
631972		CyanForces	Thousands Islands (IOI22_islands)	C++17	35 / 100	309 ms	32212 KiB

islands

#include "islands.h"

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

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define debug(...) //ignore
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef long double ld;

variant<bool, vi> find_journey(int n, int m, vi u, vi v) {
  vi dead(n);
  vector<set<int>> rg(n), g(n);
  rep(i,0,m) {
    g[u[i]].emplace(i);
    rg[v[i]].emplace(i);
  }

  queue<int> q;
  rep(x,0,n) if(sz(g[x]) == 0) q.emplace(x);

  auto del = [&](int e) {
    g[u[e]].erase(e);
    rg[v[e]].erase(e);
    if(sz(g[u[e]]) == 0) q.emplace(u[e]);
  };

  auto trim = [&]() {
    while(sz(q)) {
      int x = q.front();
      q.pop();
      dead[x] = true;
      vi es(all(rg[x]));
      for(int e : es) del(e);
    }
  };

  trim();
  if(dead[0]) return false;

  vi pth;
  int x = 0;
  int lst_e = -1;
  while(sz(g[x]) == 1) {
    assert(!dead[x]);
    pth.emplace_back(x);

    vi es(all(rg[x]));
    for(int e : es) if(e != lst_e) del(e);
    trim();
    if(dead[0]) return false;

    int e = *g[x].begin();
    x = v[e];
    lst_e = e;
  }
  assert(!dead[x]);
  assert(sz(g[x]) >= 2);

  return true;
}

• Subtask 1: 1.75 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 8.399999999999999 / 24
• Subtask 5: 15.749999999999998 / 45