Submission #203800

#	Time	Username	Problem	Language	Result	Execution time	Memory
203800		EntityIT	Sparklers (JOI17_sparklers)	C++14	50 / 100	169 ms	262148 KiB

sparklers

#include<bits/stdc++.h>

using namespace std;

#define all(x) (x).begin(), (x).end()
#define sz(x) ( (int)(x).size() )
using LL = long long;

template<class T>
inline bool asMn(T &a, const T &b) { return a > b ? a = b, true : false; }
template<class T>
inline bool asMx(T &a, const T &b) { return a < b ? a = b, true : false; }
mt19937 rng( (uint32_t)chrono::steady_clock::now().time_since_epoch().count() );

int n, k, t;
vector<int> x;

bool check(int s) {
  vector<vector<bool> > f(n, vector<bool>(n, false) );
  f[k][k] = true;
  for (int diff = 0; diff < n; ++diff) {
    for (int i = 0, j = diff; j < n; ++i, ++j) if (f[i][j]) {
      if (i && (x[j] - x[i - 1] + t - 1) / t <= 2LL * s * (j - i + 1) ) f[i - 1][j] = true;
      if (j + 1 < n && (x[j + 1] - x[i] + t - 1) / t <= 2LL * s * (j - i + 1) ) f[i][j + 1] = true;
    }
  }

  return f[0][n - 1];
}

int main() {
  ios_base::sync_with_stdio(0); cin.tie(0);

  #ifdef FourLeafClover
  freopen("input", "r", stdin);
  #endif // FourLeafCLover

  cin >> n >> k >> t; --k;
  x.assign(n, 0);
  for (auto &i : x) cin >> i;

  int l = 0, r = x.back();
  while (l < r) {
    int mid = (l + r) >> 1;
    if (check(mid) ) r = mid;
    else l = mid + 1;
  }

  cout << l << '\n';

  return 0;
}

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 0 / 50