verify/cartesian_tree.cpp

View this file on GitHub
Last update: 2026-05-30 18:08:28+09:00
Problem: https://judge.yosupo.jp/problem/cartesian_tree

Depends on

Code

// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/cartesian_tree
#include <bits/stdc++.h>
using namespace std;

#include "templates/alias.hpp"
#include "templates/macro.hpp"

#include "tree/cartesian_tree.hpp"

int main() {
  ll N;
  in(N);
  vi A(N);
  in(A);

  CartesianTree<ll> ct(A);

  vi res(N);

  rep(i, N) { res[i] = ct.par[i] == -1 ? i : ct.par[i]; }
  out(res);
}

#line 1 "verify/cartesian_tree.cpp"
// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/cartesian_tree
#include <bits/stdc++.h>
using namespace std;

#line 7 "templates/alias.hpp"

template <class T> using VC = std::vector<T>;
template <class T>
using rpriority_queue = std::priority_queue<T, VC<T>, std::greater<T>>;
using ll = long long;
using ld = long double;
using pii = std::pair<ll, ll>;
using vi = VC<ll>;
using vvi = VC<vi>;
using vvvi = VC<vvi>;
using vb = VC<bool>;
using vvb = VC<vb>;
using vf = VC<double>;
using vvf = VC<vf>;
using vpii = VC<pii>;
using vvpii = VC<vpii>;
using si = std::set<ll>;
using spii = std::set<pii>;
using mii = std::map<ll, ll>;
const std::string upperlist = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const std::string lowerlist = "abcdefghijklmnopqrstuvwxyz";
#define mp make_pair
#define dms << " " <<

constexpr int MOD998 = 998244353;
#line 4 "templates/macro.hpp"

// 引数の長さで内容が変わるrep 参考: https://trap.jp/post/1224
#define overload4(a, b, c, d, ...) d
#define _rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) overload4(__VA_ARGS__, REP, _rep)(__VA_ARGS__)
#define _rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define RREP(i, a, b) for (int i = (int)(b - 1); i >= (int)(a); i--)
#define rrep(...) overload4(__VA_ARGS__, RREP, _rrep)(__VA_ARGS__)

#define all(a) (a).begin(), (a).end()

template <typename T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T1, typename T2>
std::istream &operator>>(std::istream &is, std::pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T>
std::istream &operator>>(std::istream &is, std::vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}

template <typename T>
std::ostream &operator<<(std::ostream &os, const std::vector<T> &v) {
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  }
  return os;
}

// pythonのprintライクな関数 参考:
// https://nyaannyaan.github.io/library/template/inout.hpp
inline void out() { std::cout << std::endl; }
template <typename T, typename... U, char sep = ' '>
void out(const T &t, const U &...u) {
  std::cout << t;

  if (sizeof...(u))
    std::cout << sep;

  out(u...);
}

// cinの短縮関数 参考: https://nyaannyaan.github.io/library/template/inout.hpp
inline void in() {}
template <typename T, class... U> void in(T &t, U &...u) {
  std::cin >> t;
  in(u...);
}

template <typename T> inline T ceil_div(T a, T b) { return (a + b - 1) / b; }
template <typename T> inline T mod_pow(T a, T n, T mod) {
  T res = 1;
  while (n) {
    if (n % 2 != 0) {
      res *= a;
      res %= mod;
    }

    a *= a;
    a %= mod;

    n >>= 1;
  }

  return res;
}
template <typename T> inline T minus_mod(T a, T b) { return ((a % b) + b) % b; }

template <typename T> void apply_vec(std::vector<T> &v, T (*fn)(T)) {
  for (int i = 0; i < v.size(); i++)
    v[i] = fn(v[i]);
}
#line 7 "verify/cartesian_tree.cpp"

#line 3 "tree/cartesian_tree.hpp"

template <class Tp, class Comp = std::less<Tp>> struct CartesianTree {
  int root, n;
  std::vector<int> par, left, right;

  CartesianTree(const std::vector<Tp> &v)
      : root(-1), n{(int)v.size()}, par(n, -1), left(n, -1), right(n, -1) {
    std::stack<int> st;

    for (int i = 0; i < n; i++) {
      int top = -1;
      while (!st.empty() && Comp{}(v[i], v[st.top()])) {
        top = st.top();
        st.pop();
      }

      if (top != -1)
        left[i] = top, par[top] = i;

      if (!st.empty())
        top = st.top(), par[i] = top, right[top] = i;
      else
        root = i;

      st.emplace(i);
    }
  }
};

/**
 * @file cartesian_tree
 * @brief CartesianTree
 * @author hidehic0
 * @date 2026-05-29
 */
#line 9 "verify/cartesian_tree.cpp"

int main() {
  ll N;
  in(N);
  vi A(N);
  in(A);

  CartesianTree<ll> ct(A);

  vi res(N);

  rep(i, N) { res[i] = ct.par[i] == -1 ? i : ct.par[i]; }
  out(res);
}

Test cases

Env	Name	Status	Elapsed	Memory
g++	almost-decreasing_00	AC	370 ms	30 MB
g++	almost-decreasing_01	AC	175 ms	16 MB
g++	almost-increasing_00	AC	381 ms	31 MB
g++	almost-increasing_01	AC	180 ms	16 MB
g++	decreasing_00	AC	357 ms	30 MB
g++	decreasing_01	AC	183 ms	16 MB
g++	example_00	AC	3 ms	3 MB
g++	example_01	AC	2 ms	3 MB
g++	increasing_00	AC	336 ms	31 MB
g++	increasing_01	AC	176 ms	16 MB
g++	random_00	AC	383 ms	30 MB
g++	random_01	AC	179 ms	16 MB
g++	random_02	AC	226 ms	19 MB
g++	random_03	AC	168 ms	15 MB
g++	random_04	AC	305 ms	25 MB
g++	small_00	AC	3 ms	4 MB
g++	small_01	AC	2 ms	3 MB
g++	small_02	AC	2 ms	3 MB
g++	small_03	AC	2 ms	3 MB
g++	small_04	AC	2 ms	3 MB
g++	small_05	AC	2 ms	3 MB
g++	small_06	AC	2 ms	3 MB
g++	small_07	AC	2 ms	3 MB
g++	small_08	AC	2 ms	3 MB
g++	small_09	AC	2 ms	3 MB