14.Topological Sort Algorithm using DFS

 #include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/tree_policy.hpp>

using namespace std;

using namespace __gnu_pbds;

template <class type1>

#define ll long long int

#define endl "\n"

#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>

using ordered_multiset = tree <type1, null_type, less_equal <type1>, rb_tree_tag, tree_order_statistics_node_update>;

 //ordered_multiset <ll> kek;(declaration for multiorder set)

// ordered_set o_set;(declaration)

//kek.order_of_key(i);(strictly less then i for multi order set)

//o_set.order_of_key(5) ;(strictly less then i for multi order set)

#define yes cout << "YES\n"

#define no cout << "NO\n"

vector<ll>adj[100000];

ll vis[100000];

stack<ll>st;

void dfs(ll node)

{

     vis[node]=1;

     for(auto u:adj[node])

     {

          if(vis[u]==0)

          {

             dfs(u);

          }

     }

     st.push(node);

}

int main()

{

    ios_base::sync_with_stdio(0);

    cin.tie(0);

    cout.tie(0);

   

   ll n,m,i,j;

   cin>>n>>m;

   for(i=1;i<=m;i++)

   {

      ll u,v;

      cin>>u>>v;

      adj[u].push_back(v);

   }

  for(i=1;i<=n;i++)

  {

      if(vis[i]==0)

      {

          dfs(i);

      }

  }

   while(!st.empty())

   {

     cout<<st.top()<<" ";

     st.pop();

   }

    return 0;

}