Module org.jgrapht.core
Package org.jgrapht.generate

Class PruferTreeGenerator<V,​E>

  • Type Parameters:
    V - the graph vertex type
    E - the graph edge type
    All Implemented Interfaces:
    GraphGenerator<V,​E,​V>
    public class PruferTreeGenerator<V,​E>
extends java.lang.Object
implements GraphGenerator<V,​E,​V>
    Generates a random tree using Prüfer sequences.

    A Prüfer sequence of length $n$ is randomly generated and converted into the corresponding tree.

    This implementation is inspired by "X. Wang, L. Wang and Y. Wu, "An Optimal Algorithm for Prufer Codes," Journal of Software Engineering and Applications, Vol. 2 No. 2, 2009, pp. 111-115. doi: 10.4236/jsea.2009.22016." and has a running time of $O(n)$.

    Author:
    Alexandru Valeanu

    • Constructor Summary

      Constructors 
      Constructor Description
      PruferTreeGenerator​(int n)
      Construct a new PruferTreeGenerator.
      PruferTreeGenerator​(int[] pruferSequence)
      Construct a new PruferTreeGenerator from an input Prüfer sequence.
      PruferTreeGenerator​(int n, long seed)
      Construct a new PruferTreeGenerator.
      PruferTreeGenerator​(int n, java.util.Random rng)
      Construct a new PruferTreeGenerator

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void generateGraph​(Graph<V,​E> target, java.util.Map<java.lang.String,​V> resultMap)
      Generates a tree.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • PruferTreeGenerator

        public PruferTreeGenerator​(int[] pruferSequence)
        Construct a new PruferTreeGenerator from an input Prüfer sequence. Note that the size of the generated tree will be $l+2$ where $l$ is the length of the input sequence. The Prüfer sequence must contain integers between $0$ and $l+1$ (inclusive). Note: In this case, the same tree will be generated every time.
        Parameters:
        pruferSequence - the input Prüfer sequence
        Throws:
        java.lang.IllegalArgumentException - if n is ≤ 0
        java.lang.IllegalArgumentException - if pruferSequence is null
        java.lang.IllegalArgumentException - if pruferSequence is invalid.

      • PruferTreeGenerator

        public PruferTreeGenerator​(int n)
        Construct a new PruferTreeGenerator.
        Parameters:
        n - number of vertices to be generated
        Throws:
        java.lang.IllegalArgumentException - if n is ≤ 0

      • PruferTreeGenerator

        public PruferTreeGenerator​(int n,
                           long seed)
        Construct a new PruferTreeGenerator.
        Parameters:
        n - number of vertices to be generated
        seed - seed for the random number generator
        Throws:
        java.lang.IllegalArgumentException - if n is ≤ 0

      • PruferTreeGenerator

        public PruferTreeGenerator​(int n,
                           java.util.Random rng)
        Construct a new PruferTreeGenerator
        Parameters:
        n - number of vertices to be generated
        rng - the random number generator to use
        Throws:
        java.lang.IllegalArgumentException - if n is ≤ 0
        java.lang.NullPointerException - if rng is null

    • Method Detail

      • generateGraph

        public void generateGraph​(Graph<V,​E> target,
                          java.util.Map<java.lang.String,​V> resultMap)
        Generates a tree.

        Note: An exception will be thrown if the target graph is not empty (i.e. contains at least one vertex)

        Specified by:
        generateGraph in interface GraphGenerator<V,​E,​V>
        Parameters:
        target - the target graph
        resultMap - not used by this generator, can be null
        Throws:
        java.lang.NullPointerException - if target is null
        java.lang.IllegalArgumentException - if target is not undirected
        java.lang.IllegalArgumentException - if target is not empty