# Letter Combinations of a Phone Number

## Question

You are given a string of digits from 2-9 (inclusive), where each digit is mapped to letters based on this phone keypad layout:

Generate all unique combinations of letters that can be formed by pressing these digits on the keypad.

Input: `digits = "65"`

Output: `["mj", "mk", "ml", "nj", "nk", "nl", "oj", "ok", "ol"]`

4 can represent "m", "n", or "o" while 5 can represent "j", "k", or "l".

Input: `digits = "9"`

Output: `["w", "x", "y", "z"]`

4 can represent "w", "x", "y", "z".

## Clarify the problem

What are some questions you'd ask an interviewer?

## Understand the problem

How many unique combinations are there when digits = "59"?

5

7

9

12

All test cases pass! ðŸŽ‰

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InputExpected OutputActual Output

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