Letter Combinations of a Phone NumberMediumAcceptance Rate 56.4%Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.ExamplesExample 1Inputdigits = "23"Output["ad","ae","af","bd","be","bf","cd","ce","cf"]Constraints0 <= digits.length <= 4digits[i] is a digit in the range ["2", "9"].