Detour

input/code.cpp: In function 'void gg(int)':
input/code.cpp:21:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i=0; i<rt[c].size(); ++i){
                                ^
input/code.cpp:28:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i=0; i<rt[c].size(); ++i){
                                ^
input/code.cpp: In function 'int main()':
input/code.cpp:55:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0; i<rt[c].size(); ++i) {
                                    ^

#include <iostream>
#include <vector>
#include <queue>
#define F first
#define S second
#define MP make_pair
using namespace std;
int n, m;
vector<pair<int, int> > rt[101010];


bool u[101010];
long long d1[101010];

int e[101010];


void gg(int c){
    long long md=1222333444555666777ll;
    int mi=0;
    for (int i=0; i<rt[c].size(); ++i){
        int w=rt[c][i].F;
        if (d1[w]+rt[c][i].S<md){
            md=d1[w]+rt[c][i].S;
            mi=i;
        }
    }
    for (int i=0; i<rt[c].size(); ++i){
        if (i==mi) continue;
        int w=rt[c][i].F;
        if (u[w]) continue;
        u[w]=1;
        e[w]=c;
        gg(w);
    }
}

int main(){
    cin >> n >> m;
    for (int i=0; i<m; ++i){
        int a, b, d;
        cin >> a >> b >> d;
        rt[a].push_back(MP(b, d));
        rt[b].push_back(MP(a, d));
    }
    priority_queue<pair<long long, int> > p;
    p.push(MP(0, 1));
    while (p.size()){
        long long d=-p.top().F;
        int c=p.top().S;
        p.pop();
        if (u[c]) continue;
        u[c]=1;
        d1[c]=d;
        for (int i=0; i<rt[c].size(); ++i) {
            int w=rt[c][i].F;
            long long dd=d+rt[c][i].S;
            if (u[w]) continue;
            p.push(MP(-dd, w));
        }
    }
    for (int i=0; i<n; ++i) u[i]=0;
    for (int i=0; i<n; ++i) e[i]=-1;
    u[0]=1;
    gg(0);
    if (e[1]==-1){
        cout << "impossible\n";
    }else{
        vector<int> ans;
        int c=1;
        while (c){
            ans.push_back(c);
            c=e[c];
        }
        ans.push_back(0);
        cout << ans.size() << " ";
        for (int i=ans.size()-1; i>=0; --i) cout << ans[i] << " ";
        cout << "\n";
    }
}

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