Submission #751912

#	Time	Username	Problem	Language	Result	Execution time	Memory
751912		kenansalloum	Thousands Islands (IOI22_islands)	C++17	Compilation error	0 ms	0 KiB

islands

#include <iostream>
#include <vector>
#include <unordered_set>

using namespace std;

bool dfs(int curr, int prev, vector<vector<int>>& adjList, vector<int>& journey, unordered_set<int>& usedCanoes) {
    journey.push_back(curr);

    if (curr == 0 && journey.size() > 1) {
        return true;
    }

    for (int next : adjList[curr]) {
        if (next != prev && !usedCanoes.count(next)) {
            usedCanoes.insert(next);
            if (dfs(next, curr, adjList, journey, usedCanoes)) {
                return true;
            }
            usedCanoes.erase(next);
        }
    }

    journey.pop_back();
    return false;
}

vector<int> find_journey(int N, int M, vector<int>& U, vector<int>& V) {
    vector<vector<int>> adjList(N);

    for (int i = 0; i < M; i++) {
        adjList[U[i]].push_back(i);
        adjList[V[i]].push_back(i);
    }

    vector<int> journey;
    unordered_set<int> usedCanoes;
    dfs(0, -1, adjList, journey, usedCanoes);

    if (journey.size() <= 2000000) {
        return journey;
    } else {
        return {};
    }
}

int main() {
    int N, M;
    cin >> N >> M;

    vector<int> U(M), V(M);
    for (int i = 0; i < M; i++) {
        cin >> U[i] >> V[i];
    }

    vector<int> result = find_journey(N, M, U, V);

    if (result.empty()) {
        cout << "false" << endl;
    } else {
        cout << "true" << endl;
        cout << result.size() << endl;
        for (int i : result) {
            cout << i << " ";
        }
        cout << endl;
    }

    return 0;
}

Compilation message (stderr)

/usr/bin/ld: /tmp/ccKXue73.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccQqjev0.o:islands.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccKXue73.o: in function `main':
grader.cpp:(.text.startup+0x229): undefined reference to `find_journey(int, int, std::vector<int, std::allocator<int> >, std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status