Submission #420968

#	Time	Username	Problem	Language	Result	Execution time	Memory
420968		Hegdahl	Aliens (IOI16_aliens)	C++17	0 / 100	2074 ms	204 KiB

aliens

#include <bits/stdc++.h>
#include "aliens.h"
#define ar array

using namespace std;
using ll = long long;
using ld = long double;

int n;
vector<ar<ll, 2>> p;
vector<ll> ul, dr;

pair<ld, int> go(ld penalty) {
  ld total_cost = 0;
  int total_used = 1;

  ll cur_ul = ul[0], cur_dr = dr[0];

  ll cur_w = cur_dr-cur_ul+1;
  ld cur_cost = cur_w*cur_w;
  for (int i = 1; i < n; ++i) {
    ll extend_ul = min(cur_ul, ul[i]);
    ll extend_dr = max(cur_dr, dr[i]);
    ll extend_w = extend_dr - extend_ul + 1;
    ld extend_cost = extend_w*extend_w - cur_cost;

    ll new_w = dr[i]-ul[i]+1;
    ld new_cost = new_w*new_w + penalty;

    if (extend_cost < new_cost + i/1e8) {
      cur_cost += extend_cost;
      cur_ul = extend_ul;
      cur_dr = extend_dr;
      cur_w = extend_w;
    } else {
      total_cost += cur_cost;
      ++total_used;
      cur_cost = new_cost;
      cur_ul = ul[i];
      cur_dr = dr[i];
      cur_w = new_w;
    }
  }

  total_cost += cur_cost;

  return {total_cost, total_used};
}

long long take_photos(int n_, int m, int k, vector<int> r, vector<int> c) {
  n = n_;
  p.resize(n);
  ul.resize(n);
  dr.resize(n);

  for (int i = 0; i < n; ++i)
    p[i] = {r[i], c[i]};
  sort(p.begin(), p.end(), [&](auto a, auto b) { return min(a[0],a[1]) < min(b[0],b[1]); });

  for (int i = 0; i < n; ++i)
    ul[i] = min(p[i][0], p[i][1]);
  for (int i = 0; i < n; ++i)
    dr[i] = max(p[i][0], p[i][1]);

  /*
  cerr << "ul: ";
  for (int i = 0; i < n; ++i)
    cerr << ul[i] << " \n"[i==n-1];
  cerr << "dr: ";
  for (int i = 0; i < n; ++i)
    cerr << dr[i] << " \n"[i==n-1]; // */

  ld lo = 0, hi = 1e18;
  while (hi-lo > 1e-10) {
    ll ce = lo + (hi-lo)/2;
    auto [cost, used] = go(ce);
    if (used > k) lo = ce;
    else hi = ce;
  }

  auto [cost, used] = go(lo);
  cost -= (used-1)*lo;

  return cost;
}

• Subtask 1: 0 / 4
• Subtask 2: 0 / 12
• Subtask 3: 0 / 9
• Subtask 4: 0 / 16
• Subtask 5: 0 / 19
• Subtask 6: 0 / 40