Package org.openscience.cdk.group

Class Permutation

  • public final class Permutation
extends Object
    A permutation with some associated methods to multiply, invert, and convert to cycle strings. Much of the code in this was implemented from the C.A.G.E.S. book [Kreher, Donald and Stinson, Douglas, Combinatorial Algorithms Generation Enumeration and Search, 1998, CRC Press].
    Author:
    maclean
    Belongs to CDK module:
    group

    • Constructor Detail

      • Permutation

        public Permutation​(int size)
        Constructs an identity permutation with size elements.
        Parameters:
        size - the number of elements in the permutation

      • Permutation

        public Permutation​(int... values)
        Make a permutation from a set of values such that p[i] = x for the value x at position i.
        Parameters:
        values - the elements of the permutation

      • Permutation

        public Permutation​(Permutation other)
        Construct a permutation from another one by cloning the values.
        Parameters:
        other - the other permutation

    • Method Detail

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object

      • isIdentity

        public boolean isIdentity()
        Check to see if this permutation is the identity permutation.
        Returns:
        true if for all i, p[i] = i

      • size

        public int size()
        Get the number of elements in the permutation.
        Returns:
        the number of elements

      • get

        public int get​(int index)
        Get the value at this index.
        Parameters:
        index - the permutation value at this index.
        Returns:
        the value at this index

      • getValues

        public int[] getValues()
        Get all the values as an array.
        Returns:
        the values of the permutation

      • firstIndexOfDifference

        public int firstIndexOfDifference​(Permutation other)
        Find an r such that this[r] != other[r].
        Parameters:
        other - the other permutation to compare with
        Returns:
        the first point at which the two permutations differ

      • getOrbit

        public List<Integer> getOrbit​(int element)
        Get all the elements in the same orbit in the permutation (unsorted).
        Parameters:
        element - any element in the orbit
        Returns:
        the list of elements reachable in this permutation

      • set

        public void set​(int index,
                int value)
        Set the value at the specified index.
        Parameters:
        index - the index to set the value
        value - the value to set at this index

      • setTo

        public void setTo​(Permutation other)
        Alter a permutation by setting it to the values in the other permutation.
        Parameters:
        other - the other permutation to use
        Throws:
        IllegalArgumentException - thrown if the permutations are of different size

      • multiply

        public Permutation multiply​(Permutation other)
        Multiply this permutation by another such that for all i, this[i] = this[other[i]].
        Parameters:
        other - the other permutation to use
        Returns:
        a new permutation with the result of multiplying the permutations

      • invert

        public Permutation invert()
        Invert the permutation, so that for all i : inv[p[i]] = i.
        Returns:
        the inverse of this permutation

      • toCycleString

        public String toCycleString()
        An easily-readable version of the permutation as a product of cycles.
        Returns:
        the cycle form of the permutation as a string