finding parents of specific node in DAG

[ETH11674]

Hello everyone,
I have to write a function to find parent nodes of the given node?
my graph structure is look like this:

class Graph
{
    int V;    // No. of vertices in graph
    list<int> *adj; // Pointer to an array containing adjacency lists
 
public:
    Graph(int V);   // Constructor
    void addEdge(int u, int v);
    void parent_nodes(int Node);
};
 
Graph::Graph(int V)
{
    this->V = V;
    adj = new list<int>[V];
}
 
void Graph::addEdge(int u, int v)
{
    adj[u].push_back(v); // Add v to u’s list.
}
 
void Graph::parent_nodes(int Node)
{
    int n = 0;
    for (n; n < Node; n++) 
    {
     list <int>::iterator iter;
     for (iter = adj[n].begin(); iter != adj[n].end(); ++iter)
	if (*iter == Node)
	     cout << n << " ";
		}
}

int main()
{
Graph g(5);
		g.addEdge(0, 5);
		g.addEdge(1, 5);
		g.addEdge(2, 5);
		g.addEdge(3, 5);
		g.addEdge(0, 1);
		g.addEdge(2, 3);

		g.parent_nodes(5);
}

i have written the parent_nodes function so far but obviously it's not efficient for larger Graphs
is there any other way to do this?

i'm new to Graphs...so

any suggestions will be appreciated...

[ne555]

> for (n; n < Node; n++)
¿why do you stop at `Node' instead of traverse all the vertices?

> is there any other way to do this?
keep track of your parents
may also use an incidence matrix instead of adjacency list

[ETH11674]

why do you stop at `Node' instead of traverse all the vertices?

because all my graph nodes are sorted in Ascending order...but your right for generality
i should visit all vertices...

keep track of your parents

could you please tell me how i do this?

[ne555]

class node{
   vector<int> children;
   vector<int> parent;
};

class graph{
   vector<node> vertex;
};

void graph::addEdge(int u, int v){
   vertex[u].children.push_back(v);
   vertex[v].parent.push_back(u);
}