package ch.usi.inf.sp.graph;

import java.util.*;


public class Traversal {

    public static <G extends DiGraph<N, E>, N extends Node<E>, E extends Edge<N>>
    List<N> getNodesInReversePostOrder(final DiGraph<N, E> graph, final N entryNode) {
        final List<N> orderedNodes = getNodesInPostOrder(graph, entryNode);
        Collections.reverse(orderedNodes);
        return orderedNodes;
    }

    /**
     * From: https://eli.thegreenplace.net/2015/directed-graph-traversal-orderings-and-applications-to-data-flow-analysis/
     *
     * def postorder(graph, root):
     *   """Return a post-order ordering of nodes in the graph."""
     *   visited = set()
     *   order = []
     *   def dfs_walk(node):
     *     visited.add(node)
     *     for succ in graph.successors(node):
     *       if not succ in visited:
     *         dfs_walk(succ)
     *     order.append(node)
     *   dfs_walk(root)
     *   return order
     */
    public static <G extends DiGraph<N, E>, N extends Node<E>, E extends Edge<N>>
    List<N> getNodesInPostOrder(final DiGraph<N, E> graph, final N entryNode) {
        //TODO
        return null;
    }

    // probably add a method dfsWalk(...)

}