Problem p02904 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#include <unistd.h>

using namespace std;

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define DEBUG_VEC(v)                                                           \
  cerr << #v << ":";                                                           \
  for (int i = 0; i < v.size(); i++)                                           \
    cerr << " " << v[i];                                                       \
  cerr << endl
#define DEBUG_MAT(v)                                                           \
  cerr << #v << endl;                                                          \
  for (int i = 0; i < v.size(); i++) {                                         \
    for (int j = 0; j < v[i].size(); j++) {                                    \
      cerr << v[i][j] << " ";                                                  \
    }                                                                          \
    cerr << endl;                                                              \
  }

typedef long long ll;

#define vi vector<int>
#define vl vector<ll>
#define vii vector<vector<int>>
#define vll vector<vector<ll>>
#define vs vector<string>
#define pii pair<int, int>
#define pis pair<int, string>
#define psi pair<string, int>
#define pll pair<ll, ll>
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T> ostream &operator<<(ostream &os, pair<S, T> p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}
#define X first
#define Y second
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define rrep1(i, n) for (int i = (n); i > 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(), c.end()
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const ll MOD = 1000000007;
// const ll MOD = 998244353;
const double pi = 3.14159265358979323846;
#define Sp(p) cout << setprecision(15) << fixed << p << endl;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
int dx2[8] = {1, 1, 0, -1, -1, -1, 0, 1}, dy2[8] = {0, 1, 1, 1, 0, -1, -1, -1};
#define fio()                                                                  \
  cin.tie(0);                                                                  \
  ios::sync_with_stdio(false);
// #define mp make_pair
// #define endl '\n'

template <typename T> class SegmentTree {
public:
  using F = function<T(T &, T &)>;
  int n;
  vector<T> dat;
  T e; // 単位元
  F query_func;
  F update_func;

  SegmentTree(vector<T> a, F query_func, F update_func, T e)
      : n(a.size()), query_func(query_func), update_func(update_func), e(e) {
    dat.resize(4 * n);
    init(0, 0, n, a);
  }

  void init(int k, int l, int r, vector<T> &a) {
    if (r - l == 1) {
      dat[k] = a[l];
    } else {
      int lch = 2 * k + 1, rch = 2 * k + 2;
      init(lch, l, (l + r) / 2, a);
      init(rch, (l + r) / 2, r, a);
      dat[k] = query_func(dat[lch], dat[rch]);
    }
  }

  // k番目の値をaに変更
  void update(int k, T a, int v, int l, int r) {
    if (r - l == 1) {
      dat[v] = update_func(dat[v], a);
    } else {
      if (k < (l + r) / 2)
        update(k, a, 2 * v + 1, l, (l + r) / 2);
      else {
        update(k, a, 2 * v + 2, (l + r) / 2, r);
      }
      dat[v] = query_func(dat[v * 2 + 1], dat[v * 2 + 2]);
    }
  }

  //[a,b)の最小値を求める
  // 後ろのほうの引数は計算の簡単のための引数
  // kは接点の番号,l,rはその接点が[l,r)に対応していることを表す
  // 従って、外からはquery(a,b,0,0,n)としてよぶ
  T query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l) {
      return e;
    }
    if (a <= l && r <= b) {
      return dat[k];
    } else {
      T ul = query(a, b, k * 2 + 1, l, (l + r) / 2);
      T ur = query(a, b, k * 2 + 2, (l + r) / 2, r);
      return query_func(ul, ur);
    }
  }
};

int min_f(int a, int b) { return min(a, b); }
int max_f(int a, int b) { return max(a, b); }

int main() {
  int n, k;
  cin >> n >> k;
  vi p(n);
  rep(i, n) cin >> p[i];

  set<pii> lr;
  int l = 0, r = 1;
  int pre = p[0];
  while (r <= n) {
    if (r == n) {
      lr.insert(pii(l, r));
      break;
    }
    if (p[r] > pre) {
      pre = p[r];
      r++;
    } else {
      lr.insert(pii(l, r));
      l = r;
      r = r + 1;
      pre = p[l];
    }
  }

  SegmentTree<int> min_seg(p, min_f, min_f, inf);
  SegmentTree<int> max_seg(p, max_f, max_f, -inf);

  int ans = 1;
  bool al = false;

  auto itr = lr.begin();
  r = itr->second;
  if (r >= k) {
    al = true;
  }

  for (int i = 0; i + k < n; i++) {
    auto itr = lr.lower_bound(pii(i + 1, i + inf));
    if (itr != lr.begin()) {
      itr--;
      int l = itr->first, r = itr->second;
      if (l <= i + 1 and r >= i + 1 + k) {
        if (not al) {
          al = true;
          ans++;
        }
        continue;
      }
    }

    vi p2 = p;
    sort(p2.begin() + i, p2.begin() + i + k);
    vi p3 = p;
    sort(p3.begin() + i + 1, p3.begin() + i + k + 1);
    if (p[i] == min_seg.query(i, i + k, 0, 0, min_seg.n) and
        p[i + k] == max_seg.query(i + 1, i + k + 1, 0, 0, max_seg.n)) {
      continue;
    } else {
      ans++;
    }
  }
  cout << ans << endl;
}


Fixed submission:
#include <bits/stdc++.h>
#include <unistd.h>

using namespace std;

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define DEBUG_VEC(v)                                                           \
  cerr << #v << ":";                                                           \
  for (int i = 0; i < v.size(); i++)                                           \
    cerr << " " << v[i];                                                       \
  cerr << endl
#define DEBUG_MAT(v)                                                           \
  cerr << #v << endl;                                                          \
  for (int i = 0; i < v.size(); i++) {                                         \
    for (int j = 0; j < v[i].size(); j++) {                                    \
      cerr << v[i][j] << " ";                                                  \
    }                                                                          \
    cerr << endl;                                                              \
  }

typedef long long ll;

#define vi vector<int>
#define vl vector<ll>
#define vii vector<vector<int>>
#define vll vector<vector<ll>>
#define vs vector<string>
#define pii pair<int, int>
#define pis pair<int, string>
#define psi pair<string, int>
#define pll pair<ll, ll>
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T> ostream &operator<<(ostream &os, pair<S, T> p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}
#define X first
#define Y second
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define rrep1(i, n) for (int i = (n); i > 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(), c.end()
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const ll MOD = 1000000007;
// const ll MOD = 998244353;
const double pi = 3.14159265358979323846;
#define Sp(p) cout << setprecision(15) << fixed << p << endl;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
int dx2[8] = {1, 1, 0, -1, -1, -1, 0, 1}, dy2[8] = {0, 1, 1, 1, 0, -1, -1, -1};
#define fio()                                                                  \
  cin.tie(0);                                                                  \
  ios::sync_with_stdio(false);
// #define mp make_pair
// #define endl '\n'

template <typename T> class SegmentTree {
public:
  using F = function<T(T &, T &)>;
  int n;
  vector<T> dat;
  T e; // 単位元
  F query_func;
  F update_func;

  SegmentTree(vector<T> a, F query_func, F update_func, T e)
      : n(a.size()), query_func(query_func), update_func(update_func), e(e) {
    dat.resize(4 * n);
    init(0, 0, n, a);
  }

  void init(int k, int l, int r, vector<T> &a) {
    if (r - l == 1) {
      dat[k] = a[l];
    } else {
      int lch = 2 * k + 1, rch = 2 * k + 2;
      init(lch, l, (l + r) / 2, a);
      init(rch, (l + r) / 2, r, a);
      dat[k] = query_func(dat[lch], dat[rch]);
    }
  }

  // k番目の値をaに変更
  void update(int k, T a, int v, int l, int r) {
    if (r - l == 1) {
      dat[v] = update_func(dat[v], a);
    } else {
      if (k < (l + r) / 2)
        update(k, a, 2 * v + 1, l, (l + r) / 2);
      else {
        update(k, a, 2 * v + 2, (l + r) / 2, r);
      }
      dat[v] = query_func(dat[v * 2 + 1], dat[v * 2 + 2]);
    }
  }

  //[a,b)の最小値を求める
  // 後ろのほうの引数は計算の簡単のための引数
  // kは接点の番号,l,rはその接点が[l,r)に対応していることを表す
  // 従って、外からはquery(a,b,0,0,n)としてよぶ
  T query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l) {
      return e;
    }
    if (a <= l && r <= b) {
      return dat[k];
    } else {
      T ul = query(a, b, k * 2 + 1, l, (l + r) / 2);
      T ur = query(a, b, k * 2 + 2, (l + r) / 2, r);
      return query_func(ul, ur);
    }
  }
};

int min_f(int a, int b) { return min(a, b); }
int max_f(int a, int b) { return max(a, b); }

int main() {
  int n, k;
  cin >> n >> k;
  vi p(n);
  rep(i, n) cin >> p[i];

  set<pii> lr;
  int l = 0, r = 1;
  int pre = p[0];
  while (r <= n) {
    if (r == n) {
      lr.insert(pii(l, r));
      break;
    }
    if (p[r] > pre) {
      pre = p[r];
      r++;
    } else {
      lr.insert(pii(l, r));
      l = r;
      r = r + 1;
      pre = p[l];
    }
  }

  SegmentTree<int> min_seg(p, min_f, min_f, inf);
  SegmentTree<int> max_seg(p, max_f, max_f, -inf);

  int ans = 1;
  bool al = false;

  auto itr = lr.begin();
  r = itr->second;
  if (r >= k) {
    al = true;
  }

  for (int i = 0; i + k < n; i++) {
    auto itr = lr.lower_bound(pii(i + 1, i + inf));
    if (itr != lr.begin()) {
      itr--;
      int l = itr->first, r = itr->second;
      if (l <= i + 1 and r >= i + 1 + k) {
        if (not al) {
          al = true;
          ans++;
        }
        continue;
      }
    }

    if (p[i] == min_seg.query(i, i + k, 0, 0, min_seg.n) and
        p[i + k] == max_seg.query(i + 1, i + k + 1, 0, 0, max_seg.n)) {
      continue;
    } else {
      ans++;
    }
  }
  cout << ans << endl;
}