Problem p04052 (C++)

Buggy submission (status: Runtime Error):
//              +-- -- --++-- +-In the name of ALLAH-+ --++-- -- --+              \\

#include <bits/stdc++.h>

#define F first
#define S second
#define _sz(x) (int)x.size()

using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;

int const N = 5e5 + 20;
int n, k, a[N], res[N];
set<int> st;

pii seg[N << 2];

void modify(int p, int val, int v = 1, int s = 0, int e = n) {
  if (s + 1 == e) {
    seg[v] = pii(val, s);
    return;
  }

  int mid = (s + e) >> 1, lc = v << 1, rc = lc | 1;

  if (p < mid)
    modify(p, val, lc, s, mid);
  else
    modify(p, val, rc, mid, e);

  seg[v] = max(seg[lc], seg[rc]);
}

pii get(int l, int r, int v = 1, int s = 0, int e = n) {
  if (s >= r || e <= l)
    return pii(-1, 0);
  if (s >= l && e <= r)
    return seg[v];

  int mid = (s + e) >> 1, lc = v << 1, rc = lc | 1;

  return max(get(l, r, lc, s, mid), get(l, r, rc, mid, e));
}

inline void rel(int b) {
  int xl = b * k, xr = min(n, xl + k);

  pii p = get(xl, xr);
  int index = p.S;

  if (a[index] && p == get(max(0, index - k + 1), min(n, index + k)))
    st.insert(index);
}

int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

  cin >> n >> k;
  for (int i = 0; i < n; i++)
    cin >> a[i];

  for (int i = 0; i < n; i++)
    modify(i, a[i]);

  for (int i = 0; i < n; i += k)
    rel(i / k);

  for (int i = 0; i < n; i++) {
    int index = *st.rbegin();
    res[index] = n - i;
    st.erase(index);
    a[index] = 0;
    modify(index, a[index]);

    rel(index / k);
    if (index - k >= 0)
      rel(index / k - 1);
    if (index + k < n)
      rel(index / k + 1);
  }

  for (int i = 0; i < n; i++)
    cout << res[i] << '\n';
}


Fixed submission:
//              +-- -- --++-- +-In the name of ALLAH-+ --++-- -- --+              \\

#include <bits/stdc++.h>

#define F first
#define S second
#define _sz(x) (int)x.size()

using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;

int const N = 5e5 + 20;
int n, k, a[N], res[N];
set<int> st;

pii seg[N << 2];

void modify(int p, int val, int v = 1, int s = 0, int e = n) {
  if (s + 1 == e) {
    seg[v] = pii(val, s);
    return;
  }

  int mid = (s + e) >> 1, lc = v << 1, rc = lc | 1;

  if (p < mid)
    modify(p, val, lc, s, mid);
  else
    modify(p, val, rc, mid, e);

  seg[v] = max(seg[lc], seg[rc]);
}

pii get(int l, int r, int v = 1, int s = 0, int e = n) {
  if (s >= r || e <= l)
    return pii(-1, 0);
  if (s >= l && e <= r)
    return seg[v];

  int mid = (s + e) >> 1, lc = v << 1, rc = lc | 1;

  return max(get(l, r, lc, s, mid), get(l, r, rc, mid, e));
}

inline void rel(int b) {
  int xl = b * k, xr = min(n, xl + k);

  pii p = get(xl, xr);
  int index = p.S;

  if (a[index] && p == get(max(0, index - k + 1), min(n, index + k)))
    st.insert(index);
}

int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

  cin >> n >> k;
  for (int i = 0; i < n; i++)
    cin >> a[i];

  for (int i = 0; i < n; i++)
    modify(i, a[i]);

  for (int i = 0; i < n; i += k)
    rel(i / k);

  for (int i = 0; i < n; i++) {
    int index = *st.rbegin();
    res[index] = n - i;
    st.erase(index);
    a[index] = 0;
    modify(index, a[index]);

    int b = index / k;

    rel(b);
    if (b)
      rel(b - 1);
    if (b + 1 <= (n - 1) / k)
      rel(b + 1);
  }

  for (int i = 0; i < n; i++)
    cout << res[i] << '\n';
}