Submission #837592

#	Time	Username	Problem	Language	Result	Execution time	Memory
837592		tengiz05	Thousands Islands (IOI22_islands)	C++17	5 / 100	27 ms	4432 KiB

islands

#include "islands.h"

#include <bits/stdc++.h>

using namespace std;

std::variant<bool, vector<int>> find_journey(int n, int m, vector<int> U, vector<int> V) {
    if (n == 2) {
        vector<int> e[n];
        for (int i = 0; i < m; i++) {
            e[U[i]].push_back(i);
        }
        if (e[0].size() >= 2 && e[1].size() >= 1) {
            return vector<int>{e[0][0], e[1][0], e[0][1], e[0][0], e[1][0], e[0][1]};
        } else {
            return false;
        }
    }
    vector<vector<int>> adj(n);
    for (int i = 0; i < m; i += 2) {
        adj[U[i]].push_back(i);
    }
    vector<int> path;
    vector<int> dep(n);
    vector<int> vis(n);
    bool found = false;
    vector<int> ans;
    function<void(int)> dfs = [&](int u) {
        vis[u] = 1;
        for (int i : adj[u]) {
            if (vis[V[i]] == 2) {
                continue;
            }
            if (vis[V[i]] == 1) {
                vector<int> cycle;
                for (int j = 0; j < dep[u] - dep[V[i]]; j++) {
                    cycle.push_back(path.back());
                    path.pop_back();
                }
                reverse(cycle.begin(), cycle.end());
                cycle.push_back(i);
                for (int x : cycle) {
                    ans.push_back(x);
                }
                for (int x : cycle) {
                    ans.push_back(x ^ 1);
                }
                reverse(cycle.begin(), cycle.end());
                for (int x : cycle) {
                    ans.push_back(x);
                }
                for (int x : cycle) {
                    ans.push_back(x ^ 1);
                }
                return;
            }
            dep[V[i]] = dep[u] + 1;
            path.push_back(i);
            dfs(V[i]);
            if (found) return;
            path.pop_back();
        }
        vis[u] = 2;
    };
    dfs(0);
}

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:19:30: warning: control reaches end of non-void function [-Wreturn-type]
   19 |     vector<vector<int>> adj(n);
      |                              ^

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