verify/yosupo/tree/cartesian_tree.test.cpp

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Last update: 2025-04-16 16:21:03+07:00
Problem: https://judge.yosupo.jp/problem/cartesian_tree

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Code

#define PROBLEM "https://judge.yosupo.jp/problem/cartesian_tree"
#include "template.hpp"
#include "data-structure/cartesian-tree.hpp"

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    int n;
    cin >> n;
    vector<int> a(n);
    for(auto &x:a)cin >> x;
    CartesianTree<int,true> ct(a);
    auto ans=ct.par;
    ans[ct.root]=ct.root;
    for(auto x:ans)cout << x << " ";
}

#line 1 "verify/yosupo/tree/cartesian_tree.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/cartesian_tree"
#line 2 "template.hpp"
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

using ll = long long;
using db = long double;
using vi = vector<int>;
using vl = vector<ll>;
using vd = vector<db>;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using pdd = pair<db,db>;
const int INF=INT_MAX/2;
const int MOD=998244353;
const int MOD2=1000000007;
const ll LINF=LLONG_MAX/2;
const db DINF=numeric_limits<db>::infinity();
const db EPS=1e-9;
const db PI=acos(db(-1));

template<class T>
using ordered_set = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
template<class T>
using ordered_multiset = tree<T,null_type,less_equal<T>,rb_tree_tag,tree_order_statistics_node_update>;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng64(chrono::steady_clock::now().time_since_epoch().count());
#line 3 "data-structure/cartesian-tree.hpp"

/**
 * Author: Teetat T.
 * Date: 2025-02-20
 * Description: Cartesian Tree.
 */

template<class T,bool IS_MIN>
struct CartesianTree{
    int n;
    vector<T> &a;
    vector<pair<int,int>> range;
    vector<int> lch,rch,par;
    int root;

    CartesianTree(vector<T> &_a):n((int)_a.size()),a(_a){
        range.assign(n,{-1,-1});
        lch=rch=par=vector<int>(n,-1);
        if(n==1){
            range[0]={0,1};
            root=0;
            return;
        }
        auto cmp=[&](int i,int j)->bool {
            if(IS_MIN)a[i]>a[j]||(a[i]==a[j]&&i<j);
            return a[i]<a[j]||(a[i]==a[j]&&i<j);
        };
        vector<int> st;
        for(int i=0;i<n;i++){
            while(!st.empty()&&cmp(i,st.back())){
                lch[i]=st.back();
                st.pop_back();
            }
            range[i].first=(st.empty()?-1:st.back())+1;
            st.emplace_back(i);
        }
        for(int i=n-1;i>=0;i--){
            while(!st.empty()&&cmp(i,st.back())){
                rch[i]=st.back();
                st.pop_back();
            }
            range[i].second=(st.empty()?n:st.back())-1;
            st.emplace_back(i);
        }
        for(int i=0;i<n;i++)if(lch[i]!=-1)par[lch[i]]=i;
        for(int i=0;i<n;i++)if(rch[i]!=-1)par[rch[i]]=i;
        for(int i=0;i<n;i++)if(par[i]==-1)root=i;
    }
};
#line 4 "verify/yosupo/tree/cartesian_tree.test.cpp"

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    int n;
    cin >> n;
    vector<int> a(n);
    for(auto &x:a)cin >> x;
    CartesianTree<int,true> ct(a);
    auto ans=ct.par;
    ans[ct.root]=ct.root;
    for(auto x:ans)cout << x << " ";
}