Apr 4, 2025 · Apr 4, 2025 · Apr 4, 2025 · Apr 4, 2025 · Apr 4, 2025 · Apr 4, 2025
diff --git a/Ciphers/SubstitutionCipher.js b/Ciphers/SubstitutionCipher.js
 /**
 * Substitution Cipher
 *
 * A monoalphabetic substitution cipher replaces each letter of the plaintext
 * with another letter based on a fixed permutation (key) of the alphabet.
 * https://en.wikipedia.org/wiki/Substitution_cipher
 */

 const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
 const defaultKey = 'QWERTYUIOPASDFGHJKLZXCVBNM'

 /**
 * Encrypts a string using a monoalphabetic substitution cipher
 * @param {string} text - The text to encrypt
 * @param {string} key - The substitution key (must be 26 uppercase letters)
 * @returns {string}
 */
 export function substitutionCipherEncryption(text, key = defaultKey) {
  if (key.length !== 26 || !/^[A-Z]+$/.test(key)) {
    throw new RangeError('Key must be 26 uppercase English letters.')
  }

  let result = ''
  const textUpper = text.toUpperCase()
  for (let i = 0; i < textUpper.length; i++) {
    const char = textUpper[i]
    const index = alphabet.indexOf(char)
    if (index !== -1) {
      result += key[index]
    } else {
      result += char
    }
  }
  return result
 }
 /**
 * Decrypts a string encrypted with the substitution cipher
 * @param {string} text - The encrypted text
 * @param {string} key - The substitution key used during encryption
 * @returns {string}
 */
 export function substitutionCipherDecryption(text, key = defaultKey) {
  if (key.length !== 26 || !/^[A-Z]+$/.test(key)) {
    throw new RangeError('Key must be 26 uppercase English letters.')
  }

  let result = ''
  const textUpper = text.toUpperCase()
  for (let i = 0; i < textUpper.length; i++) {
    const char = textUpper[i]
    const index = key.indexOf(char)
    if (index !== -1) {
      result += alphabet[index]
    } else {
      result += char
    }
  }
  return result
 }
diff --git a/Ciphers/test/SubstitutionCipher.test.js b/Ciphers/test/SubstitutionCipher.test.js
 import { describe, it, expect } from 'vitest'
 import {
  substitutionCipherEncryption,
  substitutionCipherDecryption
 } from '../SubstitutionCipher.js'

 describe('Substitution Cipher', () => {
  const key = 'QWERTYUIOPASDFGHJKLZXCVBNM'

  it('correctly encrypts a message', () => {
    const encrypted = substitutionCipherEncryption('HELLO WORLD', key)
    expect(encrypted).toBe('ITSSG VGKSR')
  })

  it('correctly decrypts a message', () => {
    const decrypted = substitutionCipherDecryption('ITSSG VGKSR', key)
    expect(decrypted).toBe('HELLO WORLD')
  })

  it('handles non-alphabetic characters', () => {
    const encrypted = substitutionCipherEncryption('Test! 123', key)
    expect(encrypted).toBe('ZTLZ! 123')
  })

  it('throws error for invalid key', () => {
    expect(() => substitutionCipherEncryption('HELLO', 'BADKEY')).toThrow(
      RangeError
    )
  })
  it('encrypts using default key if none provided', () => {
    const encrypted = substitutionCipherEncryption('HELLO WORLD')
    expect(encrypted).toBe('ITSSG VGKSR')
  })

  it('decrypts using default key if none provided', () => {
    const decrypted = substitutionCipherDecryption('ITSSG VGKSR')
    expect(decrypted).toBe('HELLO WORLD')
  })

  it('throws error for invalid key in decryption', () => {
    expect(() => substitutionCipherDecryption('HELLO', 'BADKEY')).toThrow(RangeError)
  })

 })
diff --git a/Maths/MobiusFunction.js b/Maths/MobiusFunction.js
  return primeFactorsArray.length !== new Set(primeFactorsArray).size
    ? 0
    : primeFactorsArray.length % 2 === 0
    ? 1
    : -1
 ? 1
 : -1
 }
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,59 @@
		/**
		* Substitution Cipher
		*
		* A monoalphabetic substitution cipher replaces each letter of the plaintext
		* with another letter based on a fixed permutation (key) of the alphabet.
		* https://en.wikipedia.org/wiki/Substitution_cipher
		*/

		const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
		const defaultKey = 'QWERTYUIOPASDFGHJKLZXCVBNM'

		/**
		* Encrypts a string using a monoalphabetic substitution cipher
		* @param {string} text - The text to encrypt
		* @param {string} key - The substitution key (must be 26 uppercase letters)
		* @returns {string}
		*/
		export function substitutionCipherEncryption(text, key = defaultKey) {
		if (key.length !== 26 \|\| !/^[A-Z]+$/.test(key)) {
		throw new RangeError('Key must be 26 uppercase English letters.')
		}

		let result = ''
		const textUpper = text.toUpperCase()
		for (let i = 0; i < textUpper.length; i++) {
		const char = textUpper[i]
		const index = alphabet.indexOf(char)
		if (index !== -1) {
		result += key[index]
		} else {
		result += char
		}
		}
		return result
		}
		/**
		* Decrypts a string encrypted with the substitution cipher
		* @param {string} text - The encrypted text
		* @param {string} key - The substitution key used during encryption
		* @returns {string}
		*/
		export function substitutionCipherDecryption(text, key = defaultKey) {
		if (key.length !== 26 \|\| !/^[A-Z]+$/.test(key)) {
		throw new RangeError('Key must be 26 uppercase English letters.')
		}

		let result = ''
		const textUpper = text.toUpperCase()
		for (let i = 0; i < textUpper.length; i++) {
		const char = textUpper[i]
		const index = key.indexOf(char)
		if (index !== -1) {
		result += alphabet[index]
		} else {
		result += char
		}
		}
		return result
		}
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,44 @@
		import { describe, it, expect } from 'vitest'
		import {
		substitutionCipherEncryption,
		substitutionCipherDecryption
		} from '../SubstitutionCipher.js'

		describe('Substitution Cipher', () => {
		const key = 'QWERTYUIOPASDFGHJKLZXCVBNM'

		it('correctly encrypts a message', () => {
		const encrypted = substitutionCipherEncryption('HELLO WORLD', key)
		expect(encrypted).toBe('ITSSG VGKSR')
		})

		it('correctly decrypts a message', () => {
		const decrypted = substitutionCipherDecryption('ITSSG VGKSR', key)
		expect(decrypted).toBe('HELLO WORLD')
		})

		it('handles non-alphabetic characters', () => {
		const encrypted = substitutionCipherEncryption('Test! 123', key)
		expect(encrypted).toBe('ZTLZ! 123')
		})

		it('throws error for invalid key', () => {
		expect(() => substitutionCipherEncryption('HELLO', 'BADKEY')).toThrow(
		RangeError
		)
		})
		it('encrypts using default key if none provided', () => {
		const encrypted = substitutionCipherEncryption('HELLO WORLD')
		expect(encrypted).toBe('ITSSG VGKSR')
		})

		it('decrypts using default key if none provided', () => {
		const decrypted = substitutionCipherDecryption('ITSSG VGKSR')
		expect(decrypted).toBe('HELLO WORLD')
		})

		it('throws error for invalid key in decryption', () => {
		expect(() => substitutionCipherDecryption('HELLO', 'BADKEY')).toThrow(RangeError)
		})

		})
Original file line number	Diff line number	Diff line change
Expand Up		@@ -28,6 +28,6 @@ export const mobiusFunction = (number) => {
		return primeFactorsArray.length !== new Set(primeFactorsArray).size
		? 0
		: primeFactorsArray.length % 2 === 0
		? 1
		: -1
		? 1
		: -1
		}