Submission #311936

#	Time	Username	Problem	Language	Result	Execution time	Memory
311936		VROOM_VARUN	Port Facility (JOI17_port_facility)	C++14	100 / 100	1853 ms	85532 KiB

port_facility

/*
ID: varunra2
LANG: C++
TASK: ports
*/

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

#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
  cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif

#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e9
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second

const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions
int n;
VII vals;
VI par;
VI siz;
MPII mp;

void init() {
  par.resize(2 * n);
  siz.assign(2 * n, 1);
  vals.resize(n);
  iota(all(par), 0);
}

int find(int x) {
  while (par[x] != par[par[x]]) par[x] = par[par[x]];
  return par[x];
}

bool same(int x, int y) { return find(x) == find(y); }

bool merge(int x, int y) {
  x = find(x);
  y = find(y);
  if (x == y) return false;
  if (siz[x] < siz[y]) swap(x, y);
  par[y] = x;
  siz[x] += siz[y];
  return true;
}

int main() {
// #ifndef ONLINE_JUDGE
  // freopen("ports.in", "r", stdin);
  // freopen("ports.out", "w", stdout);
// #endif
  cin.sync_with_stdio(0);
  cin.tie(0);

  cin >> n;
  init();

  for (int i = 0; i < n; i++) {
    cin >> vals[i].x >> vals[i].y;
  }

  sort(all(vals));

  for (int i = 0; i < n; i++) {
    auto start = mp.lower_bound(vals[i].x);
    auto end = mp.lower_bound(vals[i].y);
    while (start != end) {
      merge(i, start->y + n);
      merge(i + n, start->y);
      if (same(start->y, prev(end)->y)) break;  // this line is important
      // it keeps it from becoming O(n ^ 2)
      start++;
    }
    mp[vals[i].y] = i;
  }

  for (int i = 0; i < n; i++) {
    if (same(i, i + n)) {
      cout << "0\n";
      return 0;
    }
  }

  ll ret = 1;

  for (int i = 0; i < n; i++) {
    if (find(i) == i) {
      ret *= 2;
      ret %= MOD;
    }
  }

  cout << ret << '\n';

  return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 56 / 56
• Subtask 4: 22 / 22