Submission #724441

#	Time	Username	Problem	Language	Result	Execution time	Memory
724441		Pety	Aliens (IOI16_aliens)	C++14	100 / 100	281 ms	13388 KiB

aliens

#include <bits/stdc++.h>
 
using namespace std;
 
const long long INF = 1e18;
vector<pair<long long, long long>>p, p2;

pair<long long, int>dp[100002];

struct line {
  long long a, b;
  int cnt;
  line (long long _a, long long _b, int _cnt): a(_a), b(_b), cnt(_cnt) {};
  long long eval (long long x) {
    return a * x + b;
  }
};


long long inter (line x, line y) {
  return (y.b - x.b) / (x.a - y.a);
} 

struct CHT {
  vector<line>q;
  vector<long long>point;
  void add(line L) {
    while (q.size() >= 2 && inter(L, q.back()) <= inter(q.back(), q.end()[-2])) {
      q.pop_back();
      point.pop_back();
    }
    q.push_back(L);
    if (q.size() >= 2)
      point.push_back(inter(q.end()[-1], q.end()[-2]));
  }
  pair<long long, int> get (long long x) {
    int st = 0, dr = point.size() - 1, ans = point.size();
    while (st <= dr) {
      int mid = (st + dr) / 2;
      if (x <= point[mid]) {
        dr = mid - 1;
        ans = mid;
      }
      else
        st = mid + 1;
    }
    return {q[ans].eval(x) + x * x, q[ans].cnt + 1};
  }
};

long long lol (int i) {
  long long x = max(0ll, p[i].second - p[i + 1].first + 1);
  return x * x;
}


void solve (int n, long long cost) {
  CHT C;
  dp[0] = {0, 0};
  C.add(line(2 - 2 * p[1].first, p[1].first * p[1].first - 2 * p[1].first + cost + 1, 0));
  for (int i = 1; i <= n; i++) {
    dp[i] = C.get(p[i].second);
    if (i < n)
      C.add(line(2 - 2 * p[i + 1].first, dp[i].first + p[i + 1].first * p[i + 1].first - 2 * p[i + 1].first + cost + 1 - lol(i), dp[i].second));
  }
}
 
long long take_photos(int n, int m, int k, vector<int>r, vector<int> c) {
  for (int i = 0; i < n; i++) {
    if (r[i] > c[i])
      swap(r[i], c[i]);
    p2.push_back({r[i], -c[i]});
  }
  sort(p2.begin(), p2.end());
  p.push_back({-1, -1});
  long long mx = -1;
  for (int i = 0; i < n; i++) {
    if (-p2[i].second > mx)
      p.push_back({p2[i].first, -p2[i].second});
    mx = max(mx, -p2[i].second);
  }
  n = p.size() - 1;
  k = min(k, n);
  long long st = 0, dr = INF, answer;
  while (st <= dr) {
    long long mid = (st + dr) / 2;
    solve(n, mid);
    if (dp[n].second <= k) {
      answer = dp[n].first - mid * k;
      dr = mid - 1;
    }
    else
      st = mid + 1;
  }
  return answer;
}
 
// int main() {
//     int n, m, k;
//     assert(3 == scanf("%d %d %d", &n, &m, &k));
 
 
//     std::vector<int> r(n), c(n);
//     for (int i = 0; i < n; i++) {
//         assert(2 == scanf("%d %d", &r[i], &c[i]));
//     }
//     long long ans = take_photos(n, m, k, r, c);
    
    
//     printf("%lld\n", ans);
//     return 0;
// }
 
/**
 5 7 2
 0 3
 4 4
 4 6
 4 5
 4 6
  
*/

Compilation message (stderr)

aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:95:10: warning: 'answer' may be used uninitialized in this function [-Wmaybe-uninitialized]
   95 |   return answer;
      |          ^~~~~~

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