Snakeless path

#include<bits/stdc++.h>
//#include<unordered_set>
// #pragma GCC optimize("Ofast")
using namespace std;
#define int long long
#define die(x) return cout << x << endl, 0
#define FI first
#define SE second
#define all(o) o.begin(), o.end()
#define endl '\n'
#define IOS ios::sync_with_stdio(0), cin.tie(0)
#define FILE freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout)
#define SZ(x) ((int)(x).size())
#define PB push_back
#define PF push_front
#define POB pop_back
#define POF pop_front
#define MP make_pair
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef map<int,int> mpi;
typedef set<int> sti;
typedef vector<pii> vii;
typedef map<pii,int> mpii;
typedef set<pii> stii;
typedef long double ld;
typedef long long ll;
int gcd(int x,int y){ return (!y ? x : gcd(y, x%y)); }
int power(int x, int y) { return (!y ? 1 : power(x, y / 2) * power(x, y / 2) * (y % 2 ? x : 1)); }
int to_int(string sconvert){stringstream geek(sconvert);int xconvert = 0; geek >> xconvert; return xconvert;}
int fastMax(int x, int y) { return (((y-x)>>(32-1))&(x^y))^y; }
int fastMin(int x, int y) { return (((y-x)>>(32-1))&(x^y))^x; }
const int MAXN=3e5+30,MAX_LOG=30,MOD=1e9+7,INF=1e17;
const double PI = acos(-1);
int mod(int x) { return (x % MOD + MOD) % MOD; }

int n, m, q;
vi blc[MAXN];

int p[MAXN];
int blc_mk[MAXN];


int curr_mk;
bool visited[MAXN];
sti not_visited;

void bfs_ish(){
    queue<int> q;
    q.push(1);
    visited[1] = true;

    while(!q.empty()){
        int curr = q.front();
        q.pop();
        curr_mk++;

        for(int nxt: blc[curr]){
            blc_mk[nxt] = curr_mk;
        }
        vi can_reach;
        for(int nxt : not_visited){
            if(blc_mk[nxt] != curr_mk){
                can_reach.PB(nxt);
            }
         }
        
         for(int nxt : can_reach){
            not_visited.erase(nxt);
            p[nxt] = curr;

            
            visited[nxt] = true;
            q.push(nxt);
        }
    }
}

int MAIN(){
    cin>>n>>m;
    for (int i = 0; i < m; i++){
        int u,v;
        cin>>u>>v;
        blc[u].PB(v);
        blc[v].PB(u);
    }

    for(int i = 2; i <= n; i++){
        not_visited.insert(i);
    }
    bfs_ish();

    if(!visited[n]){
        cout<<0<<endl;
        return 0;
    }
    vi pth;
    for(int i = n; i != 0; i = p[i]){
        pth.PB(i);
    }
    reverse(pth.begin(),pth.end());

    cout<<pth.size()<<endl;
    
    
    for(int i=0; i < SZ(pth); i++){
        cout<<pth[i]<<" ";
    }
    cout<<endl;
 

    return 0;
}

int32_t main(){
    IOS;
    int t=1;
    //cin>>t;
    while(t--)MAIN();
    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: ACCEPTED

Test 71

Verdict: ACCEPTED

Test 72

Verdict: ACCEPTED

Test 73

Verdict: ACCEPTED

Test 74

Verdict: ACCEPTED

Test 75

Verdict: ACCEPTED

Test 76

Verdict: ACCEPTED

Test 77

Verdict: ACCEPTED

Test 78

Verdict: ACCEPTED

Test 79

Verdict: ACCEPTED

Test 80

Verdict: ACCEPTED

Test 81

Verdict: ACCEPTED

Test 82

Verdict: ACCEPTED

Test 83

Verdict: ACCEPTED

Test 84

Verdict: ACCEPTED

Test 85

Verdict: ACCEPTED

Test 86

Verdict: ACCEPTED

Test 87

Verdict: ACCEPTED

Test 88

Verdict: ACCEPTED

Test 89

Verdict: ACCEPTED