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/*

*

* Letter Combinations of a Phone Number

*

* Given a string containing digits from 2-9 inclusive,

* return all possible letter combinations that the number could represent.

* Return the answer in any order.

* A mapping of digits to letters (just like on the telephone buttons) is given below.

* Note that 1 does not map to any letters.

* More info: https://leetcode.com/problems/letter-combinations-of-a-phone-number/

*/

/*

* @param {string} digits

* @returns {string[]} all the possible combinations

*/

const letterCombinations = (digits) => {

const length = digits?.length

const result = []

if (!length) {

return result

}

const digitMap = {

2: 'abc',

3: 'def',

4: 'ghi',

5: 'jkl',

6: 'mno',

7: 'pqrs',

8: 'tuv',

9: 'wxyz'

}

const combinations = (index, combination) => {

let letter

let letterIndex

if (index >= length) {

result.push(combination)

return

}

const digit = digitMap[digits[index]]

letterIndex = 0

while ((letter = digit[letterIndex++])) {

combinations(index + 1, combination + letter)

}

}

combinations(0, '')

return result

}

export { letterCombinations }