Snakeless path

// ~/.vim/cpp_template.cpp
#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <limits>

#define REP(i,a,b) for (int i = a; i < b; i++)

// Type Aliases for 1D and 2D vectors with initialization
#define vi(n, val) vector<int>(n, val) // 1D vector of ints with size n, initialized to val
#define vll(n, val) vector<long long>(n, val) // 1D vector of long longs with size n, initialized to val
#define ll long long
#define vvi(n, m, val) vector<vector<int>>(n, vector<int>(m, val)) // 2D vector of ints (n x m), initialized to val
#define vvll(n, m, val) vector<vector<long long>>(n, vector<long long>(m, val)) // 2D vector of long longs (n x m), initialized to val

#define LL_INF std::numeric_limits<long long int>::max()
#define INF std::numeric_limits<int>::max()


using namespace std;


template <typename T>
void pV(const std::vector<T>& vec, const std::string& label = "Vector") {
    std::cout << label << ": [ ";
    for (const auto& elem : vec) {
        std::cout << elem << " ";
    }
    std::cout << "]" << std::endl;
}


bool dfs(int s, int n, vector<bool> *visited, vector<int> (*adj)[], vector<int> *vals) {
    if ((*visited)[s]) return false;
    (*visited)[s] = true;
    // process node s
    if(s == n-1){
        (*vals).push_back(n-1);
        return true;
    }


    for (auto u: (*adj)[s]) {
        if(dfs(u, n, visited, adj, vals)){
            (*vals).push_back(s);
            return true;
        }

    }
    return false;
}
/*
// DEPTH-FRIRST-SEARCH
vector<int> adj[N];                                                          
vector<bool> visited(N, false);
int u, v;
for(int i = 0; i < M;i++){
    cin >> u >> v;
    u--;
    v--;
    adj[u].push_back(v);
    adj[v].push_back(u);
}
*/

vector<long long> dijkstra(int N, int x, vector<vector<pair<int,int>>> *adj){
    vector<bool> processed(N, false);
    vector<long long> distance(N, LL_INF);
    priority_queue<pair<long long,int>> q;
    //for (int i = 1; i <= n; i++) distance[i] = INF;
    distance[x] = 0;
    q.push({0,x});
    while (!q.empty()) {
        int a = q.top().second; q.pop();
        if (processed[a]) continue;
        processed[a] = true;
        for (auto u : (*adj)[a]) {
            int b = u.first, w = u.second;
            if (distance[a]+w < distance[b]) {
                distance[b] = distance[a]+w;
                q.push({-distance[b],b});
            }
        }
    }
    return distance;
}


/*
DIJKSTRA
//vector<vector<pair<int,int>>> adj(N, vector<pair<int, int>>(N));
*/



int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    // Your code starts here
    int N, m;
    cin >> N >> m;
    int n = N;

    vector<vector<int>> adj(N, vector<int>(N, 0));//, vector<pair<int, int>>(N));
    //vector<vector<int>>(n, vector<int>(m, val))
    REP(i, 0, n){
        adj[i][i] = INF;
    }
    REP(i, 0, m){
        int a, b;
        cin >> a >> b;
        a--;
        b--;
        adj[a][b] = INF;
        adj[b][a] = INF;
    }


    vector<int> adj_new[N];                                                          
    REP(i, 0, n){
        REP(j, 0, n){
            if(adj[i][j] == 0){
                adj_new[i].push_back(j);
            }
        }
    }


    vector<bool> visited(n, false);
    vector<int> vals;
    bool res = dfs(0, n, &visited, &adj_new, &vals);
    if(!res){
        cout << 0 << endl;
        return 0;
    }else{
        // print sol
        cout << vals.size() << endl;
        for(int i = (int)vals.size()-1; i >=0; i--){
            cout << vals[i] + 1 << " ";
        }
    }


    /*


    vector<long long> distance = dijkstra(N, 0, &adj);
    //pV(distance);

    REP(i, 0, N){
        cout << distance[i] << ' ';
    }
    cout << endl;
    
    */
    
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: RUNTIME ERROR

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Verdict: RUNTIME ERROR

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Verdict: RUNTIME ERROR