Submission #1082443

#	Time	Username	Problem	Language	Result	Execution time	Memory
1082443		Boas	Longest Trip (IOI23_longesttrip)	C++17	40 / 100	1022 ms	3944 KiB

longesttrip

#include "longesttrip.h"

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;

template <typename T1, typename T2>
using indexed_map = tree<T1, T2, less<T1>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T>
using indexed_set = indexed_map<T, null_type>;

#define loop(x, i) for (int i = 0; i < (x); i++)
#define loop1(x, i) for (int i = 1; i <= (x); i++)
#define rev(x, i) for (int i = (int)(x) - 1; i >= 0; i--)
#define itloop(x) for (auto it = begin(x); x != end(x); it++)
#define itrev(x) for (auto it = rbegin(x); x != rend(x); it++)
#define INF32 ((int32_t)(2e9 + 1))
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
#define removeIn(x, l) l.erase(find(ALL(l), x))
#define pb push_back
#define sz(x) (int)(x).size()
#define F first
#define S second
#define var const auto &
#define foreach(l) for (var e : l)

typedef int8_t i8;
typedef int16_t i16;
typedef int32_t i32;
typedef int64_t i64;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef tuple<int, int, int, int> iiii;
typedef vector<int> vi;
typedef vector<i32> vi32;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<vi32> vvi32;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<vii> vvii;
typedef vector<viii> vviii;
typedef set<int> si;
typedef set<ii> sii;
typedef set<iii> siii;
typedef vector<si> vsi;
typedef vector<sii> vsii;
typedef vector<vsi> vvsi;
typedef vector<string> vstr;
typedef vector<vector<string>> vvstr;
typedef vector<bool> vb;
typedef vector<vb> vvb;

vi longest_trip(int N, int D)
{
    if (D >= 2)
    {
        vi res(N);
        iota(ALL(res), 0);
        if (D == 3)
        {
            return res;
        }
        si resterend;
        loop1(N - 1, i) resterend.insert(res[i]);
        loop1(N - 1, i)
        {
            auto it = resterend.begin();
            if (are_connected({res[i - 1]}, {*it}))
            {
                res[i] = *it;
                resterend.erase(it);
            }
            else
            {
                if (resterend.size() == 1)
                {
                    res.insert(res.begin(), *it);
                    res.pop_back();
                    return res;
                }
                res[i] = *next(it);
                resterend.erase(next(it));
            }
        }
        return res;
    }
    else
    {
        vsi adj(N);
        for (int i = 0; i < N; i++)
        {
            for (int j = i + 1; j < N; j++)
            {
                if (are_connected({i}, {j}))
                {
                    // cerr << i << ' ' << j << endl;
                    adj[i].insert(j);
                    adj[j].insert(i);
                }
            }
        }
        vb vis(N);
        int cnt = 0;
        auto dfs = [&](auto &&self, int i) -> void
        {
            vis[i] = 1;
            cnt++;
            for (int j : adj[i])
            {
                if (!vis[j])
                    self(self, j);
            }
        };
        dfs(dfs, 0);
        vi res;
        if (cnt != N)
        {
            loop(N, i)
            {
                if (vis[i] == (cnt >= N / 2))
                    res.pb(i);
            }
            loop(sz(res) - 1, i) assert(adj[res[i]].count(res[i + 1]));
            return res;
        }
        deque<int> path;
        path.pb(0);
        int i2 = *adj[0].begin();
        path.pb(i2);
        int i3 = -1;
        for (int j : adj[i2])
        {
            if (j != 0)
            {
                i3 = j;
                path.pb(i3);
                break;
            }
        }
        if (i3 == -1)
        {
            for (int j : adj[0])
            {
                if (j != i2)
                {
                    i3 = j;
                    path.push_front(i3);
                    break;
                }
            }
        }
        deque<int> left;
        for (int i = 1; i < N; i++)
            if (i != i2 && i != i3)
                left.pb(i);
        while (!left.empty())
        {
            int i = left.back();
            left.pop_back();
            if (adj[i].count(path[0]))
            {
                path.push_front(i);
            }
            else if (adj[i].count(path.back()))
            {
                path.push_back(i);
            }
            else
            {
                assert(adj[path[0]].count(path.back()));
                int newBegin = -1;
                for (int j = 1; j < sz(path) - 1; j++)
                {
                    if (adj[i].count(path[j]))
                    {
                        newBegin = j;
                        break;
                    }
                }
                if (newBegin == -1)
                {
                    left.push_front(i);
                    continue;
                }
                deque<int> newPath;
                newPath.pb(i);
                for (int j = newBegin; j < sz(path); j++)
                {
                    newPath.pb(path[j]);
                }
                for (int j = 0; j < newBegin; j++)
                {
                    newPath.pb(path[j]);
                }
                path = newPath;
            }
        }
        for (int v : path)
            res.pb(v);
        assert(sz(res) == N);
        // loop(sz(res) - 1, i) assert(adj[res[i]].count(res[i + 1]));
        return res;
    }
    throw;
    return {};
}

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