Submission #897276

#	Time	Username	Problem	Language	Result	Execution time	Memory
897276		themm1	Triangles (CEOI18_tri)	C++17	100 / 100	23 ms	3184 KiB

tri

#include <bits/stdc++.h>
#include "trilib.h"
using namespace std;
// ordered set whith s.order_of_key(x) method, which returns rank of element x in set s
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
*/

// pair printing
template <class T, class U>
ostream& operator<<(ostream& out, const pair<T, U> &par) {out << "(" << par.first << "; " << par.second << ")"; return out;}
// set printing
template <class T>
ostream& operator<<(ostream& out, const set<T> &cont) { out << "{"; for(const auto &x:cont) out << x << ", "; out << "}"; return out; }
// map printing
template <class T, class U>
ostream& operator<<(ostream& out, const map<T, U> &cont) {out << "{"; for(const auto &x:cont) out << x << ", "; out << "}"; return out; }
// unordered_set printing
template <class T>
ostream& operator<<(ostream& out, const unordered_set<T> &cont) {out << "{";for(const auto &x:cont) out << x << ", ";out << "}";return out;}
// unordered_map printing
template <class T, class U>
ostream& operator<<(ostream& out, const unordered_map<T, U> &cont) {out << "{";for(const auto &x:cont) out << x << ", ";out << "}";return out;}
// vector printing
template<class T>
ostream& operator<<(ostream& out, const vector<T> &cont){ out << "[";  for (const auto &x:cont) out << x << ", ";  out << "]"; return out;}

#define print(x) cout << (x) << endl;
#define dmp(x) cerr << #x << " = " << x << endl
#define dmpn(x) cerr << #x << " = " << x << "; "
#define dmpl(x) cerr << "Line " << __LINE__ << ": " << #x << " = " << x << endl

using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
#define pb push_back
#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()
#define contains(s,x) ((s).find(x) != (s).end())
const int MOD = 998244353;

int N, root = 3;
vector<int> sorted;
random_device dev;
mt19937 rng(dev());

void dac(vector<int> &a) {
        if (a.empty()) return;
        uniform_int_distribution<int> dist(0, sz(a) - 1);
        int split = a[dist(rng)];
        vector<int> left, right;
        for (int x : a) if (x != split) {
                if (is_clockwise(root, split, x)) right.pb(x);
                else left.pb(x);
        }
        dac(left);
        sorted.pb(split);
        dac(right);
}

void solve() {
        N = get_n();
        vector<int> a;
        for (int i = 1; i <= N; i++) if (i != root) a.pb(i);
        sorted.pb(root);
        dac(a);
        vector<int> hull = { sorted[0], sorted[1] };
        for (int i = 2; i < N; i++) {
                while (!is_clockwise(hull[sz(hull) - 2], hull.back(), sorted[i])) hull.pop_back();
                hull.pb(sorted[i]);
        }
        int j = 0;
        while (sz(hull) - j > 3) {
                bool first = false, second = false;
                while (!is_clockwise(hull[sz(hull) - 2], hull.back(), hull[j])) {
                        hull.pop_back();
                        first = true;
                }
                while (!is_clockwise(hull.back(), hull[j], hull[j + 1])) {
                        j++;
                        second = true;
                }
                if (!first && !second) break;
        }
        give_answer(sz(hull) - j);
}

int32_t main() {
        ios::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);

        int t = 1;
        // cin >> t;
        while (t--) {
                solve();
        }
}

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 25 / 25