Binomial coefficient implementation (#1094)

itsAkshayDubey · web-flow · commit 644d7f7faac7 · 2022-09-08T10:14:33.000+05:30
diff --git a/Maths/BinomialCoefficient.js b/Maths/BinomialCoefficient.js
@@ -0,0 +1,31 @@
+/*
+ * 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)
+}
diff --git a/Maths/test/BinomialCoefficient.test.js b/Maths/test/BinomialCoefficient.test.js
@@ -0,0 +1,29 @@
+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)
+  })
+})
