Submission #826152

#	Time	Username	Problem	Language	Result	Execution time	Memory
826152		LittleCube	Thousands Islands (IOI22_islands)	C++17	9.10 / 100	27 ms	9624 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define F first
#define S second
using namespace std;

namespace
{
    int K;
    vector<int> path;
    int vis[100000], use[200000], p[100000], pe[100000], deg[100000];
    vector<pii> E[100000];
    void dfs(int u)
    {
        vis[u] = 1;
        for (auto [v, i] : E[u])
            if (vis[v] == 0)
            {
                p[v] = u;
                pe[v] = i;
                dfs(v);
                deg[u]++;
            }
            else if (vis[v] == 1 && v != p[u])
                use[i] = 1;
    }
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V)
{
    for (int i = 0; i < M; i++)
        E[U[i]].emplace_back(pii(V[i], i));

    p[0] = -1;
    dfs(0);
    if (*max_element(deg, deg + N) >= 2)
    {
        int k = max_element(deg, deg + N) - deg;
        vector<int> down, branch, sol;
        for (int i = 0; i < N; i++)
            if (p[i] == k)
                branch.emplace_back(pe[i]);
        while (k)
        {
            down.emplace_back(pe[k]);
            k = p[k];
        }
        reverse(down.begin(), down.end());
        sol.insert(sol.end(), down.begin(), down.end());
        for (int i : branch)
            sol.emplace_back(i), sol.emplace_back(i ^ 1);
        for (int i : branch)
            sol.emplace_back(i ^ 1), sol.emplace_back(i);
        reverse(down.begin(), down.end());
        for (int i : down)
            sol.emplace_back(i ^ 1);
        return sol;
    }
    if (*max_element(use, use + M) >= 1)
    {
        int eid = max_element(use, use + M) - use;
        int u = U[eid], v = V[eid];
        vector<int> up, vp, sol;
        while (u)
        {
            up.emplace_back(pe[u]);
            u = p[u];
        }
        while (v)
        {
            vp.emplace_back(pe[v]);
            v = p[v];
        }
        reverse(up.begin(), up.end());
        reverse(vp.begin(), vp.end());
        if (up.size() > vp.size())
            eid ^= 1, swap(up, vp);
        vp = vector<int>(vp.begin() + up.size(), vp.end());
        sol.insert(sol.end(), up.begin(), up.end());
        sol.emplace_back(eid);
        reverse(vp.begin(), vp.end());
        for (auto i : vp)
            sol.emplace_back(i ^ 1);
        reverse(vp.begin(), vp.end());
        sol.insert(sol.end(), vp.begin(), vp.end());
        sol.emplace_back(eid ^ 1);
        for (auto i : vp)
            sol.emplace_back(i ^ 1);
        sol.emplace_back(eid);
        sol.emplace_back(eid ^ 1);
        reverse(vp.begin(), vp.end());
        sol.insert(sol.end(), vp.begin(), vp.end());
        return sol;
    }
    return false;
}

Compilation message (stderr)

islands.cpp:11:9: warning: '{anonymous}::K' defined but not used [-Wunused-variable]
   11 |     int K;
      |         ^

• Subtask 1: 0 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45