Oct 7, 2022 · Oct 7, 2022 · Oct 7, 2022 · Oct 7, 2022 · Oct 10, 2022 · Oct 10, 2022
diff --git a/DIRECTORY.md b/DIRECTORY.md
  * [Problem017](Project-Euler/Problem017.js)
  * [Problem018](Project-Euler/Problem018.js)
  * [Problem020](Project-Euler/Problem020.js)
  * [Problem021](Project-Euler/Problem021.js)
  * [Problem023](Project-Euler/Problem023.js)
  * [Problem025](Project-Euler/Problem025.js)
  * [Problem028](Project-Euler/Problem028.js)
diff --git a/Project-Euler/Problem021.js b/Project-Euler/Problem021.js
 /**
 * Amicable numbers
 *
 * P.S.(Project Euler - 021):
 * Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n).
 * If d(a) = b and d(b) = a, where a ≠ b, then a and b are an amicable pair and each of a and b are called amicable numbers.
 *
 * For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110;
 * therefore d(220) = 284. The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220.
 *
 * Evaluate the sum of all the amicable numbers under 10000.
 *
 * @param {Number} maxNum
 * @returns {Number} Sum of all amicable numbers under maxNum
 */
 export const sumAmicableNums = (maxNum) => {
  const amicNums = []

  for (let i = 1; i < maxNum; i++) {
    const left = d(i)
    const right = d(left)
    if (i === right && i !== left && amicNums.indexOf(i) === -1) {
      amicNums.push(i, left)
    }
  }
  return amicNums.reduce((a, b) => a + b, 0)
 }

 const d = (num) => {
  const output = []
  for (let i = 1; i < num; i++) {
    if (num % i === 0) { output.push(i) }
  }
  return output.reduce((a, b) => a + b, 0)
 }
diff --git a/Project-Euler/test/Problem021.test.js b/Project-Euler/test/Problem021.test.js
 import { sumAmicableNums } from '../Problem021.js'

 describe('Amicable numbers', () => {
  // Project Euler Condition Check
  test('if the limit is 10000', () => {
    expect(sumAmicableNums(10000)).toBe(31626)
  })
 })
Original file line number	Diff line number	Diff line change
Expand Up		@@ -239,6 +239,7 @@
		* [Problem017](Project-Euler/Problem017.js)
		* [Problem018](Project-Euler/Problem018.js)
		* [Problem020](Project-Euler/Problem020.js)
		* [Problem021](Project-Euler/Problem021.js)
		* [Problem023](Project-Euler/Problem023.js)
		* [Problem025](Project-Euler/Problem025.js)
		* [Problem028](Project-Euler/Problem028.js)
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,35 @@
		/**
		* Amicable numbers
		*
		* P.S.(Project Euler - 021):
		* Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n).
		* If d(a) = b and d(b) = a, where a ≠ b, then a and b are an amicable pair and each of a and b are called amicable numbers.
		*
		* For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110;
		* therefore d(220) = 284. The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220.
		*
		* Evaluate the sum of all the amicable numbers under 10000.
		*
		* @param {Number} maxNum
		* @returns {Number} Sum of all amicable numbers under maxNum
		*/
		export const sumAmicableNums = (maxNum) => {
		const amicNums = []

		for (let i = 1; i < maxNum; i++) {
		const left = d(i)
		const right = d(left)
		if (i === right && i !== left && amicNums.indexOf(i) === -1) {
		amicNums.push(i, left)
		}
		}
		return amicNums.reduce((a, b) => a + b, 0)
		}

		const d = (num) => {
		const output = []
		for (let i = 1; i < num; i++) {
		if (num % i === 0) { output.push(i) }
		}
		return output.reduce((a, b) => a + b, 0)
		}
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,8 @@
		import { sumAmicableNums } from '../Problem021.js'

		describe('Amicable numbers', () => {
		// Project Euler Condition Check
		test('if the limit is 10000', () => {
		expect(sumAmicableNums(10000)).toBe(31626)
		})
		})