com.graphbuilder.math

Class PascalsTriangle

java.lang.Object

com.graphbuilder.math.PascalsTriangle

public final class PascalsTriangle
extends java.lang.Object

PascalsTriangle can be used for O(1) lookup of the nCr function.

Field Summary

Fields

Modifier and Type	Field and Description
private static double[][]	pt

Constructor Summary

Constructors

Modifier	Constructor and Description
private	PascalsTriangle()

Method Summary

Modifier and Type	Method and Description
static double	nCr(int n, int r) The nCr function returns the number of ways r things can be chosen from a set of size n.
static void	reset() Resets the internal array to the initial state to free up memory.

Methods inherited from class java.lang.Object

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

Field Detail

pt

private static double[][] pt

Constructor Detail

PascalsTriangle

private PascalsTriangle()

Method Detail

nCr

public static double nCr(int n,
                         int r)

The nCr function returns the number of ways r things can be chosen from a set of size n. Mathematically, it is defined as: n! / (r! * (n - r)!) Although the result is always a whole number, double precision is used because the maximum value a double can represent is larger than long. Thus, large returned values will only be an approximation of the actual value. If the result exceeds the capabilities of double precision then the result can be checked using Double.isInfinite(...). For example: System.out.println(PascalsTriangle.nCr(1030, 515)); // outputs: Infinity If the value of n or r is less than 0 or the value of r is greater than n then 0 is returned.

reset

public static void reset()

Resets the internal array to the initial state to free up memory.