Binomial coefficient implementation (TheAlgorithms#1094)

Author: itsAkshayDubey

Maths/BinomialCoefficient.js

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+/*
+ * Author: Akshay Dubey (https://github.com/itsAkshayDubey)
+ * Binomial Coefficient: https://en.wikipedia.org/wiki/Binomial_coefficient
+ * function to find binomial coefficient of numbers n and k.
+ * return binomial coefficient of n,k
+ */
+
+/**
+ * @function findBinomialCoefficient
+ * @description -> this function returns bonimial coefficient
+ * of two numbers n & k given by n!/((n-k)!k!)
+ * @param {number} n
+ * @param {number} k
+ * @returns {number}
+ */
+
+import { calcFactorial } from './Factorial'
+
+export const findBinomialCoefficient = (n, k) => {
+ if ((typeof n !== 'number') || (typeof k !== 'number')) {
+ throw Error('Type of arguments must be number.')
+ }
+ if (n < 0 || k < 0) {
+ throw Error('Arguments must be greater than zero.')
+ }
+ let product = 1
+ for (let i = n; i > k; i--) {
+ product *= i
+ }
+ return product / calcFactorial(n - k)
+}

Maths/test/BinomialCoefficient.test.js

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+import { findBinomialCoefficient } from '../BinomialCoefficient.js'
+
+describe('Testing findBinomialCoefficient function', () => {
+ it('should return 56', () => {
+ const binomialCoefficient = findBinomialCoefficient(8, 3)
+ expect(binomialCoefficient).toBe(56)
+ })
+
+ it('should return 10', () => {
+ const binomialCoefficient = findBinomialCoefficient(5, 2)
+ expect(binomialCoefficient).toBe(10)
+ })
+
+ it('should throw error when supplied arguments other than number', () => {
+ expect(() => { findBinomialCoefficient('eight', 'three') }).toThrow(Error)
+ })
+
+ it('should throw error when n is less than zero', () => {
+ expect(() => { findBinomialCoefficient(-1, 3) }).toThrow(Error)
+ })
+
+ it('should throw error when k is less than zero', () => {
+ expect(() => { findBinomialCoefficient(1, -3) }).toThrow(Error)
+ })
+
+ it('should throw error when n and k are less than zero', () => {
+ expect(() => { findBinomialCoefficient(-1, -3) }).toThrow(Error)
+ })
+})