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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. using ll = long long;
  4.  
  5. struct FenwickMax {
  6.     int n;
  7.     vector<int> bit;
  8.  
  9.     FenwickMax(int n = 0) { init(n); }
  10.  
  11.     void init(int n_) {
  12.         n = n_;
  13.         bit.assign(n + 1, 0);
  14.     }
  15.  
  16.     void update(int idx, int val) {
  17.         for (; idx <= n; idx += idx & -idx)
  18.             bit[idx] = max(bit[idx], val);
  19.     }
  20.  
  21.     int query(int idx) {
  22.         int res = 0;
  23.         for (; idx > 0; idx -= idx & -idx)
  24.             res = max(res, bit[idx]);
  25.         return res;
  26.     }
  27. };
  28.  
  29. int main() {
  30.     ios::sync_with_stdio(false);
  31.     cin.tie(nullptr);
  32.  
  33.     int n, k;
  34.     cin >> n >> k;
  35.     vector<ll> a(n);
  36.     for (int i = 0; i < n; i++) cin >> a[i];
  37.  
  38.     auto check = [&](ll x) -> bool {
  39.         vector<ll> L(n), R(n);
  40.         for (int i = 0; i < n; i++) {
  41.             L[i] = a[i] - 1LL * i * x;
  42.             R[i] = a[i] + 1LL * i * x;
  43.         }
  44.  
  45.         vector<ll> comp = R;
  46.         sort(comp.begin(), comp.end());
  47.         comp.erase(unique(comp.begin(), comp.end()), comp.end());
  48.  
  49.         auto getPos = [&](ll v) {
  50.             return (int)(lower_bound(comp.begin(), comp.end(), v) - comp.begin()) + 1;
  51.         };
  52.  
  53.         vector<int> ord(n);
  54.         iota(ord.begin(), ord.end(), 0);
  55.         sort(ord.begin(), ord.end(), [&](int i, int j) {
  56.             if (L[i] != L[j]) return L[i] > L[j];
  57.             if (R[i] != R[j]) return R[i] < R[j];
  58.             return i < j;
  59.         });
  60.  
  61.         FenwickMax fw((int)comp.size());
  62.         int bestAll = 0;
  63.  
  64.         for (int id : ord) {
  65.             int pos = getPos(R[id]);
  66.             int best = fw.query(pos);
  67.             int cur = best + 1;
  68.             fw.update(pos, cur);
  69.             bestAll = max(bestAll, cur);
  70.         }
  71.  
  72.         return n - bestAll <= k;
  73.     };
  74.  
  75.     ll lo = -1, hi = 2000000000LL;
  76.     while (hi - lo > 1) {
  77.         ll mid = (lo + hi) / 2;
  78.         if (check(mid)) hi = mid;
  79.         else lo = mid;
  80.     }
  81.  
  82.     cout << hi << '\n';
  83.     return 0;
  84. }
  85.  
Success #stdin #stdout 0.02s 5316KB
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stdin
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Standard input is empty
stdout
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2000000000
https://ideone.com/7fWXdt
language:
C++14 (gcc 8.3)
created:
180 days ago
visibility:
secret

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