Detour

#include<bits/stdc++.h>
using namespace std;

const int INF = RAND_MAX;
int n, m;
vector<pair<int, int> > edge[100010];
int parent[100010];
vector<long long> dist(100010);

void dijkstra(int start) {
    for (int i = 0; i < n; i++)
        parent[i] = -1;

    set<pair<int, int> > setds;
    for (int i = 0; i < n; i++)
        dist[i] = INF;

    setds.insert(make_pair(0, start));
    dist[start] = 0;

    while (!setds.empty()) {
        pair<int, int> tmp = *(setds.begin());
        setds.erase(setds.begin());

        int u = tmp.second;
        for (auto i = edge[u].begin(); i != edge[u].end(); i++){
            int v = i->first;
            int weight = i->second;
            
            if (dist[v] > dist[u] + weight) {
                if (dist[v] != INF)
                    setds.erase(setds.find(make_pair(dist[v], v)));
                parent[v] = u;
                dist[v] = dist[u] + weight;
                setds.insert(make_pair(dist[v], v));
            }
        }
    }
}

void remove(){
    for (int i = 0; i < n; i++) {
        for (auto j = edge[i].begin(); j != edge[i].end(); j++) {
            if (j->first == parent[i]) {
                j->second = INF;
                break;
            }
        }
    }
}

int main() {
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int u, v, d;
        cin >> u >> v >> d;
        edge[u].push_back(make_pair(v, d));
        edge[v].push_back(make_pair(u, d));
    }
    dijkstra(1);
    remove();
    dijkstra(0);

    if (dist[1] >= INF)
        cout << "impossible" << endl;
    else{ 
        vector<int> t;
        int u = 1;
        while (u != -1) {
            t.push_back(u);
            u = parent[u];
        }
        cout << (int) t.size();
        for (auto i = t.rbegin(); i != t.rend(); i++){
            cout << ' ' << (*i);
        }
    }
    
    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