DFS ( With Adj List)

#include <iostream>
#include <algorithm>
#include <numeric>
#include <set>
#include <queue>
#include <stack>
#include <vector>
#include <climits>
#include <string>
#include <cstdio>
#include <cmath>
#define task "TESTCODE"
using namespace std;
int n, m, s, f, Trace[100001], x, y;
vector<vector<int>> Adj;
void read()
{
   cin >> n >> m >> s >> f;
   Adj.resize(n + 1);
   for (int i = 1; i <= m; ++ i)
   {
       cin >> x >> y;
       Adj[x].push_back(y);
   }
   Trace[s] = -1;
}
void DFS (int u)
{
   for (int v : Adj[u])
   {
       if (Trace[v] == 0)
       {
           Trace[v] = u;
           DFS(v);
       }
   }
}
void solve()
{
   DFS(s);
   for (int i = 1; i <= n; ++ i)
   {
       if (Trace[i] != 0)
       {
           cout << i <<' ';
       }
   }
   cout << '\n';
   while (f != s)
   {
       cout << f << "<- ";
       f = Trace[f];
   }
   cout << s;
}
int main()
{
   ios_base::sync_with_stdio(false);
   cin.tie(nullptr);
   //freopen(task".INP", "r", stdin);
   //freopen(task".OUT", "w", stdout);
   read();
   solve();
}