Submission #1338894

#TimeUsernameProblemLanguageResultExecution timeMemory
1338894madamadam3Radio Towers (IOI22_towers)C++20
23 / 100
4054 ms8884 KiB
#include "towers.h"
#include <bits/stdc++.h>

using namespace std;
#define bg(x) (x).begin()
#define en(x) (x).end()
#define all(x) bg(x), en(x)
using vi = vector<int>;
using vvi = vector<vi>;

/*
greedy left to right (sorted order) bitset idea
(2 incompatible towers that make valid subsets of the same size theres no reason not to use the smaller one)
*/

struct SegTree {
  #define midpoint (l+(r-l)/2)
  #define is_leaf (l+1==r)
  #define left_child 2*i+1, l, midpoint
  #define right_child 2*i+2, midpoint, r
  #define root 0, 0, n

  int n; vi st, arr;
  SegTree() {}
  SegTree(int n, vi arr) : n(n), arr(arr), st(4*n, INT_MIN) {build(root);}
  int build(int i, int l, int r) {
    if (is_leaf) return st[i] = arr[l];
    return st[i] = max(build(left_child), build(right_child));
  }

  int query(int ql, int qr) {return query(root, ql, qr);}
  int query(int i, int l, int r, int ql, int qr) {
    if (qr <= l || r <= ql) return INT_MIN;
    if (ql <= l && r <= qr) return st[i];
    return max(query(left_child, ql, qr), query(right_child, ql, qr));
  }
};

struct Fenw {
  int n; vector<int> BIT;
  Fenw(int n = 0) : n(n), BIT(n, 0) {}
  int query(int idx) {
    int r = 0; for (int i = idx; i >= 0; i = (i&(i+1))-1) r += BIT[i];
    return r;
  }

  void increase(int r, int delta) {
    for (int i = r; i < n; i |= i+1) BIT[i] += delta;
  }

  void update(int l, int r, int delta) {
    increase(l, delta); increase(r+1, -delta);
  }
};

int n; vi h, idx, ridx, first_left, first_right, delta_left, delta_right;
SegTree st, st2;
void init(int N, vi H) {
  n = N; h = H; first_left.assign(n, -1), first_right.assign(n, n);
  delta_left.assign(n, 0); delta_right.assign(n, 0);
  idx.assign(n, 0); iota(all(idx), 0);
  sort(all(idx), [&](int i, int j) {return h[i] < h[j];});
  ridx.assign(n, 0); for (int i = 0; i < n; i++) ridx[idx[i]] = i;
  st = SegTree(n, H); st2 = SegTree(n, idx);
}

int le = -1, ri = -1, d = -1;
bitset<100'000> f, r;
Fenw fenw; vi rleft, rright;
int rpos(int i) {return r.size() - i - 1;}

void process(int L, int R, int D) {
  f &= 0; r &= 0;

  le = L; ri = R; d = D;
  fenw = Fenw(n+1); rleft.assign(n, 0), rright.assign(n, n-1);
  for (auto i : idx) {
    int prev = rpos(r._Find_next(rpos(i)));
    int nxt = f._Find_next(i);

    first_left[i] = prev; first_right[i] = min(n, nxt);

    int left = prev < 0 ? INT_MAX : st.query(prev, i+1) - h[i];
    int right = nxt >= n ? INT_MAX : st.query(i, nxt+1) - h[i];
    delta_left[i] = left; delta_right[i] = right;

    f.set(i), r.set(rpos(i));
  }
}

bool always = true;
int max_towers(int L, int R, int D) {
  if (d == -1 || always) process(L, R, D);

  int t = R-L+1; 
  for (int i = L; i <= R; i++) {
    int p = first_left[i], q = first_right[i];
    if ((first_left[i] >= L && delta_left[i] < D) || (first_right[i] <= R && delta_right[i] < D)) t--;
  }
  return t;
}
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