Package algs42

Class DirectedEulerianCycle

java.lang.Object
algs42.DirectedEulerianCycle
public class DirectedEulerianCycle extends Object
The DirectedEulerianCycle class represents a data type for finding an Eulerian cycle or path in a digraph. An Eulerian cycle is a cycle (not necessarily simple) that uses every edge in the digraph exactly once.

This implementation uses a nonrecursive depth-first search. The constructor takes Θ(E + V) time in the worst case, where E is the number of edges and V is the number of vertices Each instance method takes Θ(1) time. It uses Θ(V) extra space (not including the digraph).

To compute Eulerian paths in digraphs, see DirectedEulerianPath. To compute Eulerian cycles and paths in undirected graphs, see EulerianCycle and EulerianPath.

For additional documentation, see Section 4.2 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

Author:
Robert Sedgewick, Kevin Wayne, Nate Liu

  • Field Details

  • Constructor Details

    • DirectedEulerianCycle

      public DirectedEulerianCycle(Digraph G)
      Computes an Eulerian cycle in the specified digraph, if one exists.
      Parameters:
      G - the digraph

  • Method Details

    • cycle

      public Iterable<Integer> cycle()
      Returns the sequence of vertices on an Eulerian cycle.
      Returns:
      the sequence of vertices on an Eulerian cycle; null if no such cycle

    • hasEulerianCycle

      public boolean hasEulerianCycle()
      Returns true if the digraph has an Eulerian cycle.
      Returns:
      true if the digraph has an Eulerian cycle; false otherwise

    • nonIsolatedVertex

      private static int nonIsolatedVertex(Digraph G)

    • satisfiesNecessaryAndSufficientConditions

      private static boolean satisfiesNecessaryAndSufficientConditions(Digraph G)
      The code below is solely for testing correctness of the data type.

    • certifySolution

      private boolean certifySolution(Digraph G)

    • unitTest

      private static void unitTest(Digraph G, String description)

    • main

      public static void main(String[] args)
      Unit tests the DirectedEulerianCycle data type.
      Parameters:
      args - the command-line arguments