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feat: add Krishnamurthy number algorithm #1990

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feat: add Krishnamurthy number algorithm #1990

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29 changes: 29 additions & 0 deletions Maths/KrishnamurthyNumber.js
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Original file line number Diff line number Diff line change
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/**
* @function isKrishnamurthyNumber
* @description A Krishnamurthy number (also called a Strong number) is a
* number whose sum of factorials of its digits equals the number itself.
* For example, 145: 1! + 4! + 5! = 1 + 24 + 120 = 145.
* @param {number} n - A positive integer
* @returns {boolean} - True if n is a Krishnamurthy number, false otherwise
* @see https://en.wikipedia.org/wiki/Krishnamurthy_number
* @example isKrishnamurthyNumber(145) => true
* @example isKrishnamurthyNumber(40585) => true
* @example isKrishnamurthyNumber(100) => false
*/
const isKrishnamurthyNumber = (n) => {
if (!Number.isInteger(n) || n < 1) {
throw new TypeError('Input must be a positive integer')
}
const factorial = (num) => {
if (num === 0 || num === 1) return 1
let result = 1
for (let i = 2; i <= num; i++) result *= i
return result
}
const sum = String(n)
.split('')
.reduce((acc, d) => acc + factorial(Number(d)), 0)
return sum === n
}

export { isKrishnamurthyNumber }
43 changes: 43 additions & 0 deletions Maths/test/KrishnamurthyNumber.test.js
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import { isKrishnamurthyNumber } from '../KrishnamurthyNumber.js'

describe('isKrishnamurthyNumber', () => {
test('1 is a Krishnamurthy number (1!=1)', () => {
expect(isKrishnamurthyNumber(1)).toBe(true)
})

test('2 is a Krishnamurthy number (2!=2)', () => {
expect(isKrishnamurthyNumber(2)).toBe(true)
})

test('145 is a Krishnamurthy number (1!+4!+5!=145)', () => {
expect(isKrishnamurthyNumber(145)).toBe(true)
})

test('40585 is a Krishnamurthy number', () => {
expect(isKrishnamurthyNumber(40585)).toBe(true)
})

test('100 is NOT a Krishnamurthy number', () => {
expect(isKrishnamurthyNumber(100)).toBe(false)
})

test('123 is NOT a Krishnamurthy number', () => {
expect(isKrishnamurthyNumber(123)).toBe(false)
})

test('10 is NOT a Krishnamurthy number', () => {
expect(isKrishnamurthyNumber(10)).toBe(false)
})

test('throws TypeError for zero', () => {
expect(() => isKrishnamurthyNumber(0)).toThrow(TypeError)
})

test('throws TypeError for negative input', () => {
expect(() => isKrishnamurthyNumber(-145)).toThrow(TypeError)
})

test('throws TypeError for float input', () => {
expect(() => isKrishnamurthyNumber(14.5)).toThrow(TypeError)
})
})
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