BigIntegerMath binomial() function | Guava | Java

The binomial(int n, int k) method of Guava’s BigIntegerMath class returns n choose k, also known as the binomial coefficient of n and k, that is,

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

Syntax:

public static BigInteger binomial(int n, int k)

Parameters: This method takes the following parameters:

• n: The base for binomial expansion.
• k: The power for binomial expansion.

Return Value: This method returns the binomial coefficient of n and k.

Exceptions: This method throws IllegalArgumentException if n < 0, k < 0 or k > n.

Note: The result can take as much as O(k log n) space.

Below examples illustrates the BigIntegerMath.binomial() method:

Example 1:

// Java code to show implementation of
// binomial(int n, int k) method
// of Guava's BigIntegerMath class

import java.math.*;
import com.google.common.math.BigIntegerMath;

class GFG {

    // Driver code
    public static void main(String args[])
    {
        int n = 5;
        int k = 2;

        // Using binomial(int n, int k) method of
        // Guava's BigIntegerMath class
        BigInteger ans = BigIntegerMath.binomial(n, k);

        System.out.println("Binomial Coefficient of "
                           + n + " & " + k
                           + " is: " + ans);

        int n1 = 15;
        int k1 = 9;

        // Using binomial(int n, int k) method of
        // Guava's BigIntegerMath class
        BigInteger ans1 = BigIntegerMath.binomial(n1, k1);

        System.out.println("Binomial Coefficient of "
                           + n1 + " & " + k1
                           + " is: " + ans1);
    }
}

Output:

Binomial Coefficient of 5 & 2 is: 10
Binomial Coefficient of 15 & 9 is: 5005

Example 2:

// Java code to show implementation of
// binomial(int n, int k) method
// of Guava's BigIntegerMath class

import java.math.*;
import com.google.common.math.BigIntegerMath;

class GFG {

    // Driver code
    public static void main(String args[])
    {

        try {
            int n = 5;
            int k = 7;

            // Using binomial(int n, int k) method of
            // Guava's BigIntegerMath class
            // This should raise "IllegalArgumentException"
            // as k > n
            BigInteger ans = BigIntegerMath.binomial(n, k);

            System.out.println("Binomial Coefficient of"
                               + n + " & " + k
                               + " is: " + ans);
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Exception: java.lang.IllegalArgumentException: k (7) > n (5)

Reference: https://google.github.io/guava/releases/21.0/api/docs/com/google/common/math/BigIntegerMath.html#binomial-int-int-