added-ModularArithmetic-code

Maths/ModularArithmetic.js

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+import { extendedEuclideanGCD } from './ExtendedEuclideanGCD'
+
+/**
+ * https://brilliant.org/wiki/modular-arithmetic/
+ * @param {Number} arg1 first argument
+ * @param {Number} arg2 second argument
+ * @returns {Number}
+ */
+
+const MOD = 10000007
+
+const isInputValid = (arg1, arg2) => {
+ if (typeof arg1 !== 'number' || typeof arg2 !== 'number') {
+ throw new TypeError('Input must be Numbers')
+ }
+}
+
+/**
+ * Modulus is Distributive property,
+ * As a result, we separate it into numbers in order to keep it within MOD's range
+*/
+
+const add = (arg1, arg2) => {
+ isInputValid(arg1, arg2)
+ return ((arg1 % MOD) + (arg2 % MOD)) % MOD
+}
+
+const subtract = (arg1, arg2) => {
+ isInputValid(arg1, arg2)
+ // An extra MOD is added to check negative results
+ return ((arg1 % MOD) - (arg2 % MOD) + MOD) % MOD
+}
+
+const multiply = (arg1, arg2) => {
+ isInputValid(arg1, arg2)
+ return ((arg1 % MOD) * (arg2 % MOD)) % MOD
+}
+
+/**
+ *
+ * It is not Possible to find Division directly like the above methods,
+ * So we have to use the Extended Euclidean Theorem for finding Multiplicative Inverse
+ * https://github.com/TheAlgorithms/JavaScript/blob/master/Maths/ExtendedEuclideanGCD.js
+ */
+
+const divide = (arg1, arg2) => {
+ // 1st Index contains the required result
+ // The theorem may have return Negative value, we need to add MOD to make it Positive
+ return (extendedEuclideanGCD(arg1, arg2)[1] + MOD) % MOD
+}
+
+export { add, subtract, multiply, divide }

Maths/test/ModularArithmetic.test.js

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