Longest route

#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 -1e9
 
 
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;
}
 
 
void dfs(int s, vector<bool> *visited, vector<int>(*adj)[]) {
    if((*visited)[s]) return;
   (*visited)[s] = true;
    // process node s
 
 
    for(auto u:(*adj)[s]) {
        dfs(u, visited, adj);
    }
}
/*
// 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
    ll n, m;
    cin >> n >> m;
 
    vector<vector<ll>> adj(n + 1);
    vector<ll> indegree(n + 1, 0);
    vector<ll> dp(n + 1, INF);      
    vector<ll> parent(n + 1, -1);
 
    for(ll i = 0; i < m; i++) {
        ll a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        indegree[b]++;
    }
 
    queue<ll> q;
    for(ll i = 1; i <= n; i++) {
        if(indegree[i] == 0) {
            q.push(i);
        }
    }
    dp[1] = 1;
 
    while(!q.empty()) {
        ll node = q.front();
        q.pop();
        for(ll next : adj[node]) {
            if(dp[node] + 1 > dp[next]) {
                dp[next] = dp[node] + 1;
                parent[next] = node;
            }
            indegree[next]--;
            if(indegree[next] <= 0) {
                q.push(next);
            }
        }
    }
    if(dp[n] == INF) {
        cout << "IMPOSSIBLE" << endl;
        return 0;
    }
    cout << dp[n] << endl;
    stack<ll> path;
    ll current = n;
    while(current != -1) {
        path.push(current);
        current = parent[current];
    }
    cout << path.top();
    path.pop();
    while(!path.empty()) {
        cout << " " << path.top();
        path.pop();
    }
    cout << endl;
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: WRONG ANSWER

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