public void RemoveSuccesor(Node successor)
{
_successors.Remove(successor);
successor.Predecessors.Remove(this);
}
public void AddPredecessor(Node node)
{
_predecessors.Add(node);
node.Successors.Add(this);
}
private void RemoveRootAndAddNewRoots(Node root, List<Node> nextRoots)
{
foreach (var successor in new List<Node>(root.Successors))
RemoveCurrentRootAndPossiblyAddNewRoot(root, successor, nextRoots);
}
private void RemoveCurrentRootAndPossiblyAddNewRoot(Node root, Node successor, List<Node> nextRoots)
{
root.RemoveSuccesor(successor);
if (IsRoot(successor))
nextRoots.Add(successor);
}
private static bool IsRoot(Node node)
{
return node.Predecessors.Count == 0;
}
static void Main(string[] args)
{
int numberOfConnections = int.Parse(Console.ReadLine());
children = new Dictionary<int, List<Node>>();
nodes = new Dictionary<int, Node>();
for (int i = 0; i < numberOfConnections; i++)
{
string[] vertexAsString = Console.ReadLine().Split(' ');
int parent = int.Parse(vertexAsString[0]);
int child = int.Parse(vertexAsString[1]);
if (!children.ContainsKey(parent))
{
children.Add(parent, new List<Node>());
}
if (!children.ContainsKey(child))
{
children.Add(child, new List<Node>());
}
if (!nodes.ContainsKey(child))
{
Node childNode = new Node(child);
nodes.Add(child, childNode);
}
if (!nodes.ContainsKey(parent))
{
Node parentNode = new Node(parent);
nodes.Add(parent, parentNode);
}
nodes[child].NumberOfParents++;
children[parent].Add(nodes[child]);
}
List<Node> noParents = new List<Node>();
foreach (var node in nodes)
{
if (node.Value.NumberOfParents == 0)
{
noParents.Add(node.Value);
}
}
while (noParents.Count != 0)
{
var parent = noParents[0];
foreach (var child in children[parent.Val])
{
child.NumberOfParents--;
if (child.NumberOfParents == 0)
{
noParents.Add(child);
}
}
Console.WriteLine(parent.Val);
noParents.Remove(parent);
}
}