Snakeless path

#include <iostream>
#include <vector>
#include <array>
#include <string>
#include <algorithm>
#include <numeric>
#include <unordered_map>
#include <unordered_set>
#include <queue>
#include <climits>
#include <cmath>
 
//#define int long long
using namespace std;

vector<bool> visited;
vector<unordered_set<int>> adj;
int N;
vector<int> res;

bool dfs(int depth, int node)
{
    if (node == N-1)
    {
        res.push_back(node);
        return true;
    }
    visited[node] = true;
    for (int i = 0; i < N; i++)
    {

        if (!visited[i] && adj[node].find(i) == adj[node].end())
        {
            if (dfs(depth+1, i))
            {
                res.push_back(node);
                return true;
            }
        }
    }
    return false;
}

void solve() {
    int m;
    cin >> N >> m;

    visited.resize(N);
    res = vector<int>();
    adj = vector<unordered_set<int>>(N, unordered_set<int>());
    for (int i = 0; i < m; i++)
    {
        int a, b;
        cin >> a >> b;
        a--;b--;
        adj[a].insert(b);
        adj[b].insert(a);
    }
    if (!dfs(1, 0))
        cout << 0;
    else
    {
        cout << res.size() << '\n';
        for (int i = res.size() - 1; i >= 0; i--)
            cout << res[i]+1 << " ";
    }
}


 
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);

    int t = 1;
 
    //cin >> t;
 
    for (int i = 0; i < t; i++)
        solve();
 
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED

Test 41

Verdict: ACCEPTED

Test 42

Verdict: ACCEPTED

Test 43

Verdict: ACCEPTED

Test 44

Verdict: ACCEPTED

Test 45

Verdict: ACCEPTED

Test 46

Verdict: ACCEPTED

Test 47

Verdict: ACCEPTED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED

Test 50

Verdict: ACCEPTED

Test 51

Verdict: ACCEPTED

Test 52

Verdict: ACCEPTED

Test 53

Verdict: ACCEPTED

Test 54

Verdict: ACCEPTED

Test 55

Verdict: ACCEPTED

Test 56

Verdict: ACCEPTED

Test 57

Verdict: ACCEPTED

Test 58

Verdict: ACCEPTED

Test 59

Verdict: ACCEPTED

Test 60

Verdict: ACCEPTED

Test 61

Verdict: ACCEPTED

Test 62

Verdict: ACCEPTED

Test 63

Verdict: ACCEPTED

Test 64

Verdict: ACCEPTED

Test 65

Verdict: ACCEPTED

Test 66

Verdict: ACCEPTED

Test 67

Verdict: ACCEPTED

Test 68

Verdict: ACCEPTED

Test 69

Verdict: ACCEPTED

Test 70

Verdict: TIME LIMIT EXCEEDED

Test 71

Verdict: TIME LIMIT EXCEEDED

Test 72

Verdict: TIME LIMIT EXCEEDED

Test 73

Verdict: TIME LIMIT EXCEEDED

Test 74

Verdict: TIME LIMIT EXCEEDED

Test 75

Verdict: ACCEPTED

Test 76

Verdict: TIME LIMIT EXCEEDED

Test 77

Verdict: ACCEPTED

Test 78

Verdict: TIME LIMIT EXCEEDED

Test 79

Verdict: ACCEPTED

Test 80

Verdict: TIME LIMIT EXCEEDED

Test 81

Verdict: TIME LIMIT EXCEEDED

Test 82

Verdict: TIME LIMIT EXCEEDED

Test 83

Verdict: TIME LIMIT EXCEEDED

Test 84

Verdict: TIME LIMIT EXCEEDED

Test 85

Verdict: TIME LIMIT EXCEEDED

Test 86

Verdict: ACCEPTED

Test 87

Verdict: ACCEPTED

Test 88

Verdict: TIME LIMIT EXCEEDED

Test 89

Verdict: ACCEPTED