com.numericalmethod.suanshu.number.big
Class BigIntegerUtils

java.lang.Object
  com.numericalmethod.suanshu.number.big.BigIntegerUtils

public class BigIntegerUtils
extends java.lang.Object

This class collects a set of utility functions for the java class BigInteger.

See Also:

Class BigInteger

Method Summary

static java.math.BigInteger	combination(int n, int k) Compute the combination function/binomial coefficient.
static java.math.BigInteger	factorial(int n) Compute the n factorial.
static java.math.BigInteger	permutation(int n, int k) Compute the permutation function.

Methods inherited from class java.lang.Object

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

Method Detail

factorial

public static java.math.BigInteger factorial(int n)

Compute the n factorial.

Parameters:

n - an integer

Returns:

n!

See Also:

Wikipedia: Factorial

combination

public static java.math.BigInteger combination(int n,
                                               int k)

Compute the combination function/binomial coefficient. It is the number of k-combinations (each of size k) from a set S with n elements (size n).

Parameters:

n - the size of the full set

k - the size of a combination

Returns:

n! / (n-k)! / k!

See Also:

Wikipedia: Combination

permutation

public static java.math.BigInteger permutation(int n,
                                               int k)

Compute the permutation function. It is the number of k-permutations (each of size k) from a set S with n elements (size n).

Parameters:

n - the size of the full set

k - the size of a permutation

Returns:

n! / (n-k)!

See Also:

Wikipedia: Permutation