Multi-Language (Coding): Mapping Digits to Letters Test

Given a string of digits, the problem requires generating all possible letter combinations that can be formed using the given digits. The input string contains only digits 2-9 inclusive. The output is a list of all possible letter combinations that the given number could represent.

To solve the problem, we can use a recursive approach. At each level of recursion, we consider the next digit in the input string and add all possible letters corresponding to that digit to each of the existing combinations. This results in the formation of new combinations. We continue this process until we have processed all the digits in the input string. Finally, we return the list of all generated combinations. Note that the base case of recursion is when we have processed all the digits in the input string.