Submission #826053

#	Time	Username	Problem	Language	Result	Execution time	Memory
826053		LittleCube	Thousands Islands (IOI22_islands)	C++17	24 / 100	34 ms	11852 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, vis, use, edge;
    vector<pii> E[100000], R[100000];
    int dfs(int u)
    {
        vis[u] = 1;
        path.emplace_back(u);
        for (auto [v, i] : E[u])
            if (vis[v] == 0 && !use[i])
            {
                edge.emplace_back(i);
                int res = dfs(v);
                if (res != -1)
                    return res;
                edge.pop_back();
            }
            else if (vis[v] == 1 && !use[i])
            {
                edge.emplace_back(i);
                path.emplace_back(v);
                return v;
            }
        path.pop_back();
        vis[u] = 2;
        return -1;
    }
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V)
{
    for (int i = 0; i < M; i += 2)
        E[U[i]].emplace_back(pii(V[i], i));

    vis.resize(N, 0);
    use.resize(M, 0);
    int res = dfs(0);
    if (res == -1)
        return false;
    vector<int> chain, cyc;
    vector<int> chE, cycE;
    {
        int i = 0;
        for (; i < path.size(); i++)
        {
            chain.emplace_back(i);
            if (path[i] == res)
                break;
            chE.emplace_back(edge[i]);
        }

        for (; i + 1 < path.size(); i++)
            cycE.emplace_back(edge[i]);
        path.clear();
    }
    vector<int> sol;
    for (int t = 0; t <= 1; t++)
    {
        sol.insert(sol.end(), chE.begin(), chE.end());
        sol.insert(sol.end(), cycE.begin(), cycE.end());
        reverse(chE.begin(), chE.end());
        sol.insert(sol.end(), chE.begin(), chE.end());
        reverse(chE.begin(), chE.end());
        for (int &i : chE)
            i ^= 1;
        for (int &i : cycE)
            i ^= 1;
        sol.insert(sol.end(), chE.begin(), chE.end());
        sol.insert(sol.end(), cycE.begin(), cycE.end());
        reverse(chE.begin(), chE.end());
        sol.insert(sol.end(), chE.begin(), chE.end());
        reverse(chE.begin(), chE.end());
        for (int &i : chE)
            i ^= 1;
        for (int &i : cycE)
            i ^= 1;
        reverse(cycE.begin(), cycE.end());
    }
    return sol;
}

Compilation message (stderr)

islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:53:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |         for (; i < path.size(); i++)
      |                ~~^~~~~~~~~~~~~
islands.cpp:61:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |         for (; i + 1 < path.size(); i++)
      |                ~~~~~~^~~~~~~~~~~~~
islands.cpp: At global scope:
islands.cpp:11:9: warning: '{anonymous}::K' defined but not used [-Wunused-variable]
   11 |     int K;
      |         ^

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