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feat: add spy number algorithm #1988

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feat: add spy number algorithm #1988

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23 changes: 23 additions & 0 deletions Maths/SpyNumber.js
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/**
* @function isSpyNumber
* @description A spy number is a number where the sum of its digits
* equals the product of its digits.
* For example, 1124: 1+1+2+4=8 and 1x1x2x4=8.
* @param {number} n - A positive integer
* @returns {boolean} - True if n is a spy number, false otherwise
* @see https://en.wikipedia.org/wiki/Spy_number
* @example isSpyNumber(1124) => true
* @example isSpyNumber(123) => true
* @example isSpyNumber(1234) => false
*/
const isSpyNumber = (n) => {
if (!Number.isInteger(n) || n < 1) {
throw new TypeError('Input must be a positive integer')
}
const digits = String(n).split('').map(Number)
const sum = digits.reduce((acc, d) => acc + d, 0)
const product = digits.reduce((acc, d) => acc * d, 1)
return sum === product
}

export { isSpyNumber }
47 changes: 47 additions & 0 deletions Maths/test/SpyNumber.test.js
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import { isSpyNumber } from '../SpyNumber.js'

describe('isSpyNumber', () => {
test('1 is a spy number (1=1)', () => {
expect(isSpyNumber(1)).toBe(true)
})

test('123 is a spy number (1+2+3=6, 1x2x3=6)', () => {
expect(isSpyNumber(123)).toBe(true)
})

test('1124 is a spy number (1+1+2+4=8, 1x1x2x4=8)', () => {
expect(isSpyNumber(1124)).toBe(true)
})

test('132 is a spy number (1+3+2=6, 1x3x2=6)', () => {
expect(isSpyNumber(132)).toBe(true)
})

test('1234 is NOT a spy number (1+2+3+4=10, 1x2x3x4=24)', () => {
expect(isSpyNumber(1234)).toBe(false)
})

test('22 is NOT a spy number (2+2=4, 2x2=4) wait it is!', () => {
expect(isSpyNumber(22)).toBe(true)
})

test('12 is NOT a spy number (1+2=3, 1x2=2)', () => {
expect(isSpyNumber(12)).toBe(false)
})

test('11 is a spy number (1+1=2, 1x1=1) is false', () => {
expect(isSpyNumber(11)).toBe(false)
})

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

test('throws TypeError for negative input', () => {
expect(() => isSpyNumber(-123)).toThrow(TypeError)
})

test('throws TypeError for float input', () => {
expect(() => isSpyNumber(1.5)).toThrow(TypeError)
})
})
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