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

#include <bits/stdc++.h>
using namespace std;
#define REP(i, x, n) for (int i = x; i < (int)n; i++)
#define rep(i, n) REP(i, 0, n)
#define sp(p) cout << setprecision(16) << fixed << p << endl;
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define SORT(a) sort(all(a))
#define RSORT(a) sort(rall(a))
#define UNIQ(a) unique(all(a))
#define UNIQNUM(a) UNIQ(a) - a.begin()
#define UNIQIT(a) a.erase(UNIQ(a), a.end());
#define VOUT(v, i)                                                             \\
  rep(i, v.size()) cout << v[i] << (i == v.size() - 1 ? "\\n" : " ");
#define vout(v) VOUT(v, z);
#define vdbg(v, i)                                                             \\
  cout << #v << ": ";                                                          \\
  for (int i = 0; i < (int)v.size(); i++) {                                    \\
    cout << v[i] << " ";                                                       \\
  }                                                                            \\
  cout << "\\n";
#define vmin(v) *min_element(all(v))
#define vmax(v) *max_element(all(v))
#define vsum(v) accumulate(all(v), 0LL)
#define MOUT(m, r, c)                                                          \\
  rep(i, r) {                                                                  \\
    rep(j, c) { cout << m[i][j] << " "; }                                      \\
    cout << endl;                                                              \\
  }
#define mout(m) MOUT(m, m.size(), m[0].size())
#define debg(a) cout << #a << ": " << a << endl;
#define out(a) debg(a);
#define aout(a)                                                                \\
  for (auto &e : a)                                                            \\
    cout << e << " ";
#define show(a)                                                                \\
  for (cont & y : a) {                                                         \\
    for (cont & x : y) {                                                       \\
      cout << x << " ";                                                        \\
    }                                                                          \\
    cout << endl;                                                              \\
  }
#define digit(a) to_string(a).length();
// template<class T>inline int out(const T &t){ print(t); putchar('\\n'); return
// 0; } template<class T>inline T gcd(T a,T b){if(b==0)return a;
// return(gcd(b,a%b));} template<class T>inline T lcm(T a,T b){return
// a/gcd(a,b)*b;}
bool is_palindrome(string s) { return s == string(s.rbegin(), s.rend()); }
#define popcount __builtin_popcount
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<vector<ll>> VV;
// const long long MOD=1000000007;
const long long INF = 1e18;
#define EPS (1e-7)
#define PI (acos(-1))
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

namespace internal {

// @param n `0 <= n`
// @return minimum non-negative `x` s.t. `n <= 2**x`
int ceil_pow2(int n) {
  int x = 0;
  while ((1U << x) < (unsigned int)(n))
    x++;
  return x;
}

// @param n `1 <= n`
// @return minimum non-negative `x` s.t. `(n & (1 << x)) != 0`
int bsf(unsigned int n) {
#ifdef _MSC_VER
  unsigned long index;
  _BitScanForward(&index, n);
  return index;
#else
  return __builtin_ctz(n);
#endif
}

} // namespace internal

template <class S, S (*op)(S, S), S (*e)()> struct segtree {
public:
  segtree() : segtree(0) {}
  segtree(int n) : segtree(std::vector<S>(n, e())) {}
  segtree(const std::vector<S> &v) : _n(int(v.size())) {
    log = internal::ceil_pow2(_n);
    size = 1 << log;
    d = std::vector<S>(2 * size, e());
    for (int i = 0; i < _n; i++)
      d[size + i] = v[i];
    for (int i = size - 1; i >= 1; i--) {
      update(i);
    }
  }

  void set(int p, S x) {
    assert(0 <= p && p < _n);
    p += size;
    d[p] = x;
    for (int i = 1; i <= log; i++)
      update(p >> i);
  }

  S get(int p) {
    assert(0 <= p && p < _n);
    return d[p + size];
  }

  S prod(int l, int r) {
    assert(0 <= l && l <= r && r <= _n);
    S sml = e(), smr = e();
    l += size;
    r += size;

    while (l < r) {
      if (l & 1)
        sml = op(sml, d[l++]);
      if (r & 1)
        smr = op(d[--r], smr);
      l >>= 1;
      r >>= 1;
    }
    return op(sml, smr);
  }

  S all_prod() { return d[1]; }

  template <bool (*f)(S)> int max_right(int l) {
    return max_right(l, [](S x) { return f(x); });
  }
  template <class F> int max_right(int l, F f) {
    assert(0 <= l && l <= _n);
    assert(f(e()));
    if (l == _n)
      return _n;
    l += size;
    S sm = e();
    do {
      while (l % 2 == 0)
        l >>= 1;
      if (!f(op(sm, d[l]))) {
        while (l < size) {
          l = (2 * l);
          if (f(op(sm, d[l]))) {
            sm = op(sm, d[l]);
            l++;
          }
        }
        return l - size;
      }
      sm = op(sm, d[l]);
      l++;
    } while ((l & -l) != l);
    return _n;
  }

  template <bool (*f)(S)> int min_left(int r) {
    return min_left(r, [](S x) { return f(x); });
  }
  template <class F> int min_left(int r, F f) {
    assert(0 <= r && r <= _n);
    assert(f(e()));
    if (r == 0)
      return 0;
    r += size;
    S sm = e();
    do {
      r--;
      while (r > 1 && (r % 2))
        r >>= 1;
      if (!f(op(d[r], sm))) {
        while (r < size) {
          r = (2 * r + 1);
          if (f(op(d[r], sm))) {
            sm = op(d[r], sm);
            r--;
          }
        }
        return r + 1 - size;
      }
      sm = op(d[r], sm);
    } while ((r & -r) != r);
    return 0;
  }

private:
  int _n, size, log;
  std::vector<S> d;

  void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); }
};

int max_op(int a, int b) { return max(a, b); };
int e() { return 0; };

int main() {
  long long N;
  scanf("%lld", &N);
  long long K;
  scanf("%lld", &K);
  std::vector<long long> A(N);
  for (int i = 0; i < N; i++) {
    scanf("%lld", &A[i]);
  }
  segtree<int, max_op, e> st(3e6 + 1);
  int ans = 0;
  for (long long i = 0; i < N; i++) {
    int l = max(A[i] - K, 0LL);
    int r = max(A[i] + K + 1, 0LL);
    int tmp = 1 + st.prod(l, r);
    st.set(A[i], max(st.get(A[i]), tmp));
    ans = max(ans, tmp);
  }
  cout << ans << endl;
  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define REP(i, x, n) for (int i = x; i < (int)n; i++)
#define rep(i, n) REP(i, 0, n)
#define sp(p) cout << setprecision(16) << fixed << p << endl;
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define SORT(a) sort(all(a))
#define RSORT(a) sort(rall(a))
#define UNIQ(a) unique(all(a))
#define UNIQNUM(a) UNIQ(a) - a.begin()
#define UNIQIT(a) a.erase(UNIQ(a), a.end());
#define VOUT(v, i)                                                             \\
  rep(i, v.size()) cout << v[i] << (i == v.size() - 1 ? "\\n" : " ");
#define vout(v) VOUT(v, z);
#define vdbg(v, i)                                                             \\
  cout << #v << ": ";                                                          \\
  for (int i = 0; i < (int)v.size(); i++) {                                    \\
    cout << v[i] << " ";                                                       \\
  }                                                                            \\
  cout << "\\n";
#define vmin(v) *min_element(all(v))
#define vmax(v) *max_element(all(v))
#define vsum(v) accumulate(all(v), 0LL)
#define MOUT(m, r, c)                                                          \\
  rep(i, r) {                                                                  \\
    rep(j, c) { cout << m[i][j] << " "; }                                      \\
    cout << endl;                                                              \\
  }
#define mout(m) MOUT(m, m.size(), m[0].size())
#define debg(a) cout << #a << ": " << a << endl;
#define out(a) debg(a);
#define aout(a)                                                                \\
  for (auto &e : a)                                                            \\
    cout << e << " ";
#define show(a)                                                                \\
  for (cont & y : a) {                                                         \\
    for (cont & x : y) {                                                       \\
      cout << x << " ";                                                        \\
    }                                                                          \\
    cout << endl;                                                              \\
  }
#define digit(a) to_string(a).length();
// template<class T>inline int out(const T &t){ print(t); putchar('\\n'); return
// 0; } template<class T>inline T gcd(T a,T b){if(b==0)return a;
// return(gcd(b,a%b));} template<class T>inline T lcm(T a,T b){return
// a/gcd(a,b)*b;}
bool is_palindrome(string s) { return s == string(s.rbegin(), s.rend()); }
#define popcount __builtin_popcount
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<vector<ll>> VV;
// const long long MOD=1000000007;
const long long INF = 1e18;
#define EPS (1e-7)
#define PI (acos(-1))
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

namespace internal {

template <class E> struct csr {
  std::vector<int> start;
  std::vector<E> elist;
  csr(int n, const std::vector<std::pair<int, E>> &edges)
      : start(n + 1), elist(edges.size()) {
    for (auto e : edges) {
      start[e.first + 1]++;
    }
    for (int i = 1; i <= n; i++) {
      start[i] += start[i - 1];
    }
    auto counter = start;
    for (auto e : edges) {
      elist[counter[e.first]++] = e.second;
    }
  }
};

// Reference:
// R. Tarjan,
// Depth-First Search and Linear Graph Algorithms
struct scc_graph {
public:
  scc_graph(int n) : _n(n) {}

  int num_vertices() { return _n; }

  void add_edge(int from, int to) { edges.push_back({from, {to}}); }

  // @return pair of (# of scc, scc id)
  std::pair<int, std::vector<int>> scc_ids() {
    auto g = csr<edge>(_n, edges);
    int now_ord = 0, group_num = 0;
    std::vector<int> visited, low(_n), ord(_n, -1), ids(_n);
    visited.reserve(_n);
    auto dfs = [&](auto self, int v) -> void {
      low[v] = ord[v] = now_ord++;
      visited.push_back(v);
      for (int i = g.start[v]; i < g.start[v + 1]; i++) {
        auto to = g.elist[i].to;
        if (ord[to] == -1) {
          self(self, to);
          low[v] = std::min(low[v], low[to]);
        } else {
          low[v] = std::min(low[v], ord[to]);
        }
      }
      if (low[v] == ord[v]) {
        while (true) {
          int u = visited.back();
          visited.pop_back();
          ord[u] = _n;
          ids[u] = group_num;
          if (u == v)
            break;
        }
        group_num++;
      }
    };
    for (int i = 0; i < _n; i++) {
      if (ord[i] == -1)
        dfs(dfs, i);
    }
    for (auto &x : ids) {
      x = group_num - 1 - x;
    }
    return {group_num, ids};
  }

  std::vector<std::vector<int>> scc() {
    auto ids = scc_ids();
    int group_num = ids.first;
    std::vector<int> counts(group_num);
    for (auto x : ids.second)
      counts[x]++;
    std::vector<std::vector<int>> groups(ids.first);
    for (int i = 0; i < group_num; i++) {
      groups[i].reserve(counts[i]);
    }
    for (int i = 0; i < _n; i++) {
      groups[ids.second[i]].push_back(i);
    }
    return groups;
  }

private:
  int _n;
  struct edge {
    int to;
  };
  std::vector<std::pair<int, edge>> edges;
};

} // namespace internal

struct two_sat {
public:
  two_sat() : _n(0), scc(0) {}
  two_sat(int n) : _n(n), _answer(n), scc(2 * n) {}

  void add_clause(int i, bool f, int j, bool g) {
    assert(0 <= i && i < _n);
    assert(0 <= j && j < _n);
    scc.add_edge(2 * i + (f ? 0 : 1), 2 * j + (g ? 1 : 0));
    scc.add_edge(2 * j + (g ? 0 : 1), 2 * i + (f ? 1 : 0));
  }
  bool satisfiable() {
    auto id = scc.scc_ids().second;
    for (int i = 0; i < _n; i++) {
      if (id[2 * i] == id[2 * i + 1])
        return false;
      _answer[i] = id[2 * i] < id[2 * i + 1];
    }
    return true;
  }
  std::vector<bool> answer() { return _answer; }

private:
  int _n;
  std::vector<bool> _answer;
  internal::scc_graph scc;
};

int main() {
  long long N;
  scanf("%lld", &N);
  long long K;
  scanf("%lld", &K);
  std::vector<long long> A(N);
  for (int i = 0; i < N; i++) {
    scanf("%lld", &A[i]);
  }
  two_sat ts(N);
  for (int i = 0; i < N; i++) {
    for (int j = i + 1; j < N; j++) {
      if (abs(A[i] - A[j]) < K) {
        ts.add_clause(i, true, j, true);
      }
    }
  }
  ts.satisfiable();
  // out(ts.satisfiable());
  // vout(ts.answer());
  vector<bool> v = ts.answer();
  // int cnt=0;
  // for (long long i = 0; i < N; i++) {
  //     if(v[i]) cnt++;
  // }
  int ret = vsum(v);
  cout << ret << endl;
  return 0;
}