Submission #746774

#	Time	Username	Problem	Language	Result	Execution time	Memory
746774		math_rabbit_1028	Thousands Islands (IOI22_islands)	C++17	35 / 100	281 ms	24996 KiB

islands

#include "islands.h"
 
#include <bits/stdc++.h>
using namespace std;
 
bool ans = false;
 
int n, m;
vector< pair<int, int> > adj[101010], rev[101010];
int out[101010], in[101010], remain[202020];
 
set< pair<int, int> > outset;
 
int ch[202020];
void DFS(int v) {
  int cnt = 0;
  for (int i = 0; i < adj[v].size(); i++) {
    if (remain[adj[v][i].second] == 0) continue;
    if (ch[adj[v][i].first] == 0) {
      cnt++;
    }
  }
  if (cnt >= 2) {
    ans = true;
    return;
  }
  for (int i = 0; i < adj[v].size(); i++) {
    if (remain[adj[v][i].second] == 0) continue;
    if (ch[adj[v][i].first] == 0) {
      ch[adj[v][i].first] = 1;
      DFS(adj[v][i].first);
    }
  }
}

std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {
  n = N; m = M;
  for (int i = 0; i < m; i++) {
    adj[U[i]].push_back({V[i], i});
    rev[V[i]].push_back({U[i], i});
    out[U[i]]++;
    in[V[i]]++;
    remain[i] = 1;
  }
 
  for (int i = 0; i < n; i++) outset.insert({out[i], i});
  while (!outset.empty() && outset.begin()->first == 0) {
    int v = outset.begin()->second;
    outset.erase(outset.begin());
    for (int i = 0; i < rev[v].size(); i++) {
      if (remain[rev[v][i].second] == 0) continue;
      remain[rev[v][i].second] = 0;
      outset.erase(outset.find(make_pair(out[rev[v][i].first], rev[v][i].first)));
      out[rev[v][i].first]--;
      outset.insert(make_pair(out[rev[v][i].first], rev[v][i].first));
    }
  }

  if (out[0] <= 1) {
    for (int i = 0; i < rev[0].size(); i++) {
      if (remain[rev[0][i].second] == 0) continue;
      remain[rev[0][i].second] = 0;
      outset.erase(outset.find(make_pair(out[rev[0][i].first], rev[0][i].first)));
      out[rev[0][i].first]--;
      outset.insert(make_pair(out[rev[0][i].first], rev[0][i].first));
    }
  }
  
  while (!outset.empty() && outset.begin()->first == 0) {
    int v = outset.begin()->second; 
    outset.erase(outset.begin());
    for (int i = 0; i < rev[v].size(); i++) {
      if (remain[rev[v][i].second] == 0) continue;
      remain[rev[v][i].second] = 0;
      outset.erase(outset.find(make_pair(out[rev[v][i].first], rev[v][i].first)));
      out[rev[v][i].first]--;
      outset.insert(make_pair(out[rev[v][i].first], rev[v][i].first));
    }
  }

  //for (int i = 0; i < m; i++) cout << remain[i] << "\n";
  //cout << "\n";
 
  ch[0] = 1;
  DFS(0);
 
  return ans;
}

Compilation message (stderr)

islands.cpp: In function 'void DFS(int)':
islands.cpp:17:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |   for (int i = 0; i < adj[v].size(); i++) {
      |                   ~~^~~~~~~~~~~~~~~
islands.cpp:27:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |   for (int i = 0; i < adj[v].size(); i++) {
      |                   ~~^~~~~~~~~~~~~~~
islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:51:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   51 |     for (int i = 0; i < rev[v].size(); i++) {
      |                     ~~^~~~~~~~~~~~~~~
islands.cpp:61:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |     for (int i = 0; i < rev[0].size(); i++) {
      |                     ~~^~~~~~~~~~~~~~~
islands.cpp:73:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   73 |     for (int i = 0; i < rev[v].size(); i++) {
      |                     ~~^~~~~~~~~~~~~~~

• 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