Problem p02537 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

template <class Monoid> struct SegTree {
  using Func = function<Monoid(Monoid, Monoid)>;
  const Func F;
  const Monoid UNITY;
  int SIZE_R;
  vector<Monoid> dat;

  SegTree(int n, const Func f, const Monoid &unity) : F(f), UNITY(unity) {
    init(n);
  }
  void init(int n) {
    SIZE_R = 1;
    while (SIZE_R < n)
      SIZE_R *= 2;
    dat.assign(SIZE_R * 2, UNITY);
  }

  /* set, a is 0-indexed */
  void set(int a, const Monoid &v) { dat[a + SIZE_R] = v; }
  void build() {
    for (int k = SIZE_R - 1; k > 0; --k)
      dat[k] = F(dat[k * 2], dat[k * 2 + 1]);
  }

  /* update a, a is 0-indexed */
  void update(int a, const Monoid &v) {
    int k = a + SIZE_R;
    dat[k] = v;
    while (k >>= 1)
      dat[k] = F(dat[k * 2], dat[k * 2 + 1]);
  }

  /* get [a, b), a and b are 0-indexed */
  Monoid get(int a, int b) {
    Monoid vleft = UNITY, vright = UNITY;
    for (int left = a + SIZE_R, right = b + SIZE_R; left < right;
         left >>= 1, right >>= 1) {
      if (left & 1)
        vleft = F(vleft, dat[left++]);
      if (right & 1)
        vright = F(dat[--right], vright);
    }
    return F(vleft, vright);
  }
  inline Monoid operator[](int a) { return dat[a + SIZE_R]; }

  /* debug */
  void print() {
    for (int i = 0; i < SIZE_R; ++i) {
      cout << (*this)[i];
      if (i != SIZE_R - 1)
        cout << ",";
    }
    cout << endl;
  }
};

int solve(int N, int K) {
  const int MAX = 510000;
  auto func = [&](int a, int b) { return max(a, b); };
  SegTree<int> seg(MAX, func, 0);
  for (int i = 0; i < N; i++) {
    int a;
    cin >> a;
    int left = max(0, a - K);
    int right = min(MAX, a + K + 1);
    int val = seg.get(left, right);
    seg.update(a, val + 1);
  }
  return seg.get(0, MAX);
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, k;
  cin >> n >> k;
  cout << solve(n, k) << endl;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

template <class Monoid> struct SegTree {
  using Func = function<Monoid(Monoid, Monoid)>;
  const Func F;
  const Monoid UNITY;
  int SIZE_R;
  vector<Monoid> dat;

  SegTree(int n, const Func f, const Monoid &unity) : F(f), UNITY(unity) {
    init(n);
  }
  void init(int n) {
    SIZE_R = 1;
    while (SIZE_R < n)
      SIZE_R *= 2;
    dat.assign(SIZE_R * 2, UNITY);
  }

  /* set, a is 0-indexed */
  void set(int a, const Monoid &v) { dat[a + SIZE_R] = v; }
  void build() {
    for (int k = SIZE_R - 1; k > 0; k--) {
      dat[k] = F(dat[k * 2], dat[k * 2 + 1]);
    }
  }

  /*update a, a is 0-indexed */
  void update(int a, const Monoid &v) {
    int k = a + SIZE_R;
    dat[k] = v;
    while (k >>= 1)
      dat[k] = F(dat[k * 2], dat[k * 2 + 1]);
  }

  /* get [a, b), a and b are 0-indexed */
  Monoid get(int a, int b) {
    Monoid vleft = UNITY, vright = UNITY;
    for (int left = a + SIZE_R, right = b + SIZE_R; left < right;
         left >>= 1, right >= 1) {
      if (left & 1)
        vleft = F(vleft, dat[left++]);
      if (right & 1)
        vright = F(dat[--right], vright);
    }
    return F(vleft, vright);
  }
  inline Monoid operator[](int a) { return dat[a + SIZE_R]; }

  /* debug */
  void print() {
    for (int i = 0; i < SIZE_R; i++) {
      cout << (*this)[i];
      if (i != SIZE_R - 1)
        cout << ",";
    }
    cout << endl;
  }
};

int solve(int N, int K) {
  const int MAX = 510000;
  auto func = [&](int a, int b) { return max(a, b); };
  SegTree<int> seg(MAX, func, 0);
  for (int i = 0; i < N; i++) {
    int a;
    cin >> a;
    int left = max(0, a - K);
    int right = min(MAX, a + K + 1);
    int val = seg.get(left, right);
    seg.update(a, val + 1);
  }
  return seg.get(0, MAX);
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, k;
  cin >> n >> k;
  cout << solve(n, k) << endl;
}