de.flexiprovider.common.math.linearalgebra
Class Permutation

java.lang.Object
  |
  +--de.flexiprovider.common.math.linearalgebra.Permutation

public class Permutation

extends java.lang.Object

This class implements permutations of the set {0,1,...,n-1} for some given n > 0, i.e., ordered sequences containing each number m (0 <= m < n) once and only once.

Author:

Elena Klintsevich, Andrei Pyshkin

Constructor Summary

Permutation(byte[] enc)
Create a permutation from an encoded permutation.

Permutation(int n)
Create the identity permutation of the given size.

Permutation(int[] perm)
Create a permutation using the given permutation vector.

Permutation(int n, SecureRandom sr)
Create a random permutation of the given size.

Method Summary

Permutation	computeInverse() Compute the inverse permutation P-1.
boolean	equals(java.lang.Object other) checks if given object is equal to this permutation.
byte[]	getEncoded() Encode this permutation as byte array.
int[]	getVector()
int	hashCode()
Permutation	rightMultiply(Permutation p) Compute the product of this permutation and another permutation.
java.lang.String	toString()

Methods inherited from class java.lang.Object

, clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Permutation

public Permutation(int n)

Create the identity permutation of the given size.

Parameters:

n - the size of the permutation

Permutation

public Permutation(int[] perm)

Create a permutation using the given permutation vector.

Parameters:

perm - the permutation vector

Permutation

public Permutation(byte[] enc)

Create a permutation from an encoded permutation.

Parameters:

enc - the encoded permutation

Permutation

public Permutation(int n,
                   SecureRandom sr)

Create a random permutation of the given size.

Parameters:

n - the size of the permutation

sr - the source of randomness

Method Detail

getEncoded

public byte[] getEncoded()

Encode this permutation as byte array.

Returns:

the encoded permutation

getVector

public int[] getVector()

Returns:

the permutation vector (perm(0),perm(1),...,perm(n-1))

computeInverse

public Permutation computeInverse()

Compute the inverse permutation P^-1.

Returns:

this^-1

rightMultiply

public Permutation rightMultiply(Permutation p)

Compute the product of this permutation and another permutation.

Parameters:

p - the other permutation

Returns:

this * p

equals

public boolean equals(java.lang.Object other)

checks if given object is equal to this permutation.

The method returns false whenever the given object is not permutation.

Overrides:

equals in class java.lang.Object

Parameters:

other - - permutation

Returns:

true or false

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

Returns:

a human readable form of the permutation

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

Returns:

the hash code of this permutation