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Commit 6f9a8e4

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added-ModularArithmetic-code (TheAlgorithms#1217)
* added-ModularArithmetic-code * fix-typo * suggested changes
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‎Maths/ModularArithmetic.js

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import { extendedEuclideanGCD } from './ExtendedEuclideanGCD'
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/**
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* https://brilliant.org/wiki/modular-arithmetic/
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* @param {Number} arg1 first argument
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* @param {Number} arg2 second argument
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* @returns {Number}
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*/
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export class ModRing {
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constructor (MOD) {
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this.MOD = MOD
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}
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isInputValid = (arg1, arg2) => {
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if (!this.MOD) {
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throw new Error('Modulus must be initialized in the object constructor')
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}
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if (typeof arg1 !== 'number' || typeof arg2 !== 'number') {
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throw new TypeError('Input must be Numbers')
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}
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}
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/**
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* Modulus is Distributive property,
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* As a result, we separate it into numbers in order to keep it within MOD's range
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*/
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add = (arg1, arg2) => {
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this.isInputValid(arg1, arg2)
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return ((arg1 % this.MOD) + (arg2 % this.MOD)) % this.MOD
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}
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subtract = (arg1, arg2) => {
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this.isInputValid(arg1, arg2)
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// An extra MOD is added to check negative results
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return ((arg1 % this.MOD) - (arg2 % this.MOD) + this.MOD) % this.MOD
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}
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multiply = (arg1, arg2) => {
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this.isInputValid(arg1, arg2)
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return ((arg1 % this.MOD) * (arg2 % this.MOD)) % this.MOD
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}
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/**
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*
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* It is not Possible to find Division directly like the above methods,
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* So we have to use the Extended Euclidean Theorem for finding Multiplicative Inverse
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* https://github.com/TheAlgorithms/JavaScript/blob/master/Maths/ExtendedEuclideanGCD.js
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*/
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divide = (arg1, arg2) => {
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// 1st Index contains the required result
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// The theorem may have return Negative value, we need to add MOD to make it Positive
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return (extendedEuclideanGCD(arg1, arg2)[1] + this.MOD) % this.MOD
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}
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}

‎Maths/test/ModularArithmetic.test.js

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import { ModRing } from '../ModularArithmetic'
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describe('Modular Arithmetic', () => {
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const MOD = 10000007
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let ring
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beforeEach(() => {
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ring = new ModRing(MOD)
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})
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describe('add', () => {
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it('Should return 9999993 for 10000000 and 10000000', () => {
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expect(ring.add(10000000, 10000000)).toBe(9999993)
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})
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it('Should return 9999986 for 10000000 and 20000000', () => {
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expect(ring.add(10000000, 20000000)).toBe(9999986)
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})
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})
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describe('subtract', () => {
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it('Should return 1000000 for 10000000 and 9000000', () => {
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expect(ring.subtract(10000000, 9000000)).toBe(1000000)
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})
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it('Should return 7 for 10000000 and 20000000', () => {
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expect(ring.subtract(10000000, 20000000)).toBe(7)
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})
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})
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describe('multiply', () => {
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it('Should return 1000000 for 100000 and 10000', () => {
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expect(ring.multiply(100000, 10000)).toBe(9999307)
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})
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it('Should return 7 for 100000 and 10000100', () => {
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expect(ring.multiply(10000000, 20000000)).toBe(98)
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})
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})
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describe('divide', () => {
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it('Should return 4 for 3 and 11', () => {
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expect(ring.divide(3, 11)).toBe(4)
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})
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it('Should return 2 for 18 and 7', () => {
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expect(ring.divide(18, 7)).toBe(2)
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})
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})
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})

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