Submission #1080634

#	Time	Username	Problem	Language	Result	Execution time	Memory
1080634		shmax	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	550 ms	984 KiB

longesttrip

#include "longesttrip.h"
#include "bits/stdc++.h"

using namespace std;
#define len(x) (int)(x.size())
#define all(x) x.begin(), x.end()
#define inf 1000'000'000'000'000'000LL
#define bit(x, i) (((x) >> i) & 1)


template<typename T>
using vec = vector<T>;

std::vector<int> longest_trip(int n, int d) {
    mt19937 rnd(14345);
    if (d == 3) {
        vec<int> ans(n);
        iota(all(ans), 0);
        return ans;
    }
    if (d == 2) {
        deque<int> ans;
        int cur = 0;
        ans.push_back(cur);
        set<int> not_used;
        for (int i = 1; i < n; i++) {
            not_used.insert(i);
        }
        while (true) {
            if (not_used.empty()) break;
            vec<int> next(all(not_used));
            int nxt = next[0];
            if (are_connected({cur}, {nxt})) {
                ans.push_back(nxt);
                not_used.erase(nxt);
                cur = nxt;
            } else {
                if (next.size() == 1) {
                    ans.push_front(next[0]);
                    break;
                } else {
                    int net = next[1];
                    ans.push_back(net);
                    not_used.erase(net);
                    cur = net;
                }
            }
        }
        return vec<int>(all(ans));
    } else {

        auto attempt = [&]() {
            deque<int> ans;
            int cur = rnd() % n;
            ans.push_back(cur);
            set<int> not_used;
            for (int i = 0; i < n; i++) {
                if (i != cur) not_used.insert(i);
            }
            auto try_find = [&](int v) {
                vec<int> t(all(not_used));
                if (!are_connected({v}, t)) return -1;
                shuffle(all(t), rnd);
                int tl = 0;
                int tr = len(t) - 1;
                auto get_part = [&](int f) {
                    vec<int> r;
                    for (int i = 0; i <= f; i++)
                        r.push_back(t[i]);
                    return r;
                };
                while (tl != tr) {
                    int tm = (tl + tr) / 2;
                    if (are_connected({v}, get_part(tm))) {
                        tr = tm;
                    } else {
                        tl = tm + 1;
                    }
                }
                return  t[tl];
            };

            while (true) {
                if (not_used.empty()) break;
                int u = try_find(ans.back());
                if (u == -1) break;
                ans.push_back(u);
                not_used.erase(u);
            }
            while (true) {
                if (not_used.empty()) break;
                int u = try_find(ans.front());
                if (u == -1) break;
                ans.push_front(u);
                not_used.erase(u);
            }
            return vec<int>(all(ans));
        };
        int T = 10;
        vec<int> best;
        while (T--) {
            auto g = attempt();
            if (len(g) > len(best))
                best = g;
            if(len(best) == n) break;
        }
        return best;
    }
}

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 60