Submission #1365769

#TimeUsernameProblemLanguageResultExecution timeMemory
1365769avighnaRadio Towers (IOI22_towers)C++20
0 / 100
4075 ms8560 KiB
#include <bits/stdc++.h>

using namespace std;

namespace {
int N;
vector<int> H;

using int64 = long long;

const int64 inf = 1e15;

class segment_tree {
  int n;
  vector<int64> seg;

public:
  segment_tree(int n) : n(n), seg(2 * n, -inf) {}

  void set(int i, int64 x) {
    for (seg[i += n] = x, i >>= 1; i > 0; i >>= 1) {
      seg[i] = max(seg[2 * i], seg[2 * i + 1]);
    }
  }

  int64 query(int l, int r) {
    int64 ans = -inf;
    for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
      if (l & 1) ans = max(ans, seg[l++]);
      if (r & 1) ans = max(ans, seg[--r]);
    }
    return ans;
  }
};
} // namespace

void init(int N, vector<int> H) {
  ::N = N, ::H = H;
}

int max_towers(int L, int R, int D) {
  vector<int> h;
  for (int i = L; i <= R; ++i) {
    h.push_back(H[i]);
  }
  const int n = R - L + 1;
  segment_tree st(n);
  for (int i = 0; i < n; ++i) {
    st.set(i, h[i]);
  }

  vector<int> ahead(n, n - 1);
  for (int i = 0; i < n; ++i) {
    if (i + 2 > n) continue;
    ahead[i] = *ranges::partition_point(views::iota(i + 2, n), [&](int j) {
      int val = st.query(i + 1, j - 1) - D;
      return h[i] <= val;
    }) - 1;
  }
  vector<vector<int>> remove(n + 1);
  for (int i = 0; i < n; ++i) {
    remove[ahead[i] + 1].push_back(i);
  }

  vector<int64> dp(n);
  segment_tree active_dp(n);
  for (int i = 0; i < n; ++i) {
    active_dp.set(i, dp[i]);
  }
  vector<bool> active(n, true);
  for (int i = 0; i < n; ++i) {
    for (int &j : remove[i]) {
      active[j] = false;
      active_dp.set(j, -inf);
    }
    dp[i] = 1;
    if (0 <= i - 2) {
      int j = *ranges::partition_point(views::iota(0, i - 2), [&](int j) {
        int val = st.query(j + 1, i - 1) - D;
        return h[i] > val;
      });
      if (j <= i - 2) {
        dp[i] = max(dp[i], active_dp.query(j, i - 2) + 1);
      }
    }
    if (active[i]) {
      active_dp.set(i, dp[i]);
    }
  }
  return int(*max_element(dp.begin(), dp.end()));
}
#Result Execution timeMemoryGrader output
Fetching results...
#Result Execution timeMemoryGrader output
Fetching results...
#Result Execution timeMemoryGrader output
Fetching results...
#Result Execution timeMemoryGrader output
Fetching results...
#Result Execution timeMemoryGrader output
Fetching results...
#Result Execution timeMemoryGrader output
Fetching results...
#Result Execution timeMemoryGrader output
Fetching results...