Submission #883199

#	Time	Username	Problem	Language	Result	Execution time	Memory
883199		MilosMilutinovic	Sparklers (JOI17_sparklers)	C++14	100 / 100	37 ms	3928 KiB

sparklers

#include <bits/stdc++.h>
 
using namespace std;
 
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k, t;
  cin >> n >> k >> t;
  --k;
  vector<int> x(n);
  for (int i = 0; i < n; i++) {
    cin >> x[i];
  }
  auto Check = [&](long long s) {
    if (2 * s * t >= (long long) 1e9) {
      return true;
    }
    vector<long long> L;
    vector<long long> R;
    for (int i = k; i >= 0; i--) {
      L.push_back(x[i] - 2 * s * t * i);
    }
    for (int i = k; i < n; i++) {
      R.push_back(x[i] - 2 * s * t * i);
    }
    {
      int i = 0, j = 0;
      long long mx = L[0];
      long long mn = R[0];
      while (i < (int) L.size() || j < (int) R.size()) {
        if (i < (int) L.size() && L[i] >= mn) {
          mx = max(mx, L[i]);
          i += 1;
          continue;
        }
        if (j < (int) R.size() && R[j] <= mx) {
          mn = min(mn, R[j]);
          j += 1;
          continue;
        }
        break;
      }
      if (i != (int) L.size() || j != (int) R.size()) {
        return false;
      } 
    }
    reverse(L.begin(), L.end());
    reverse(R.begin(), R.end());
    {
      if (L[0] < R[0]) {
        return false;
      }
      int i = 0, j = 0;
      long long mx = L[0];
      long long mn = R[0];
      while (i < (int) L.size() || j < (int) R.size()) {
        if (i < (int) L.size() && L[i] >= mn) {
          mx = max(mx, L[i]);
          i += 1;
          continue;
        }
        if (j < (int) R.size() && R[j] <= mx) {
          mn = min(mn, R[j]);
          j += 1;
          continue;
        }
        break;
      }
      if (i != (int) L.size() || j != (int) R.size()) {
        return false;
      }
    }
    return true;
  };
  long long low = 0, high = 1e9, ans = -1;
  while (low <= high) {
    long long mid = low + high >> 1;
    if (Check(mid)) {
      ans = mid;
      high = mid - 1;
    } else {
      low = mid + 1;
    }
  }
  cout << ans << '\n';
  return 0;
}

Compilation message (stderr)

sparklers.cpp: In function 'int main()':
sparklers.cpp:78:25: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   78 |     long long mid = low + high >> 1;
      |                     ~~~~^~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 50 / 50