Given a string of digits from 2 to 9, return every letter combination the digits could represent, using the letters on a phone keypad: 2 is abc, 3 is def, 4 is ghi, 5 is jkl, 6 is mno, 7 is pqrs, 8 is tuv and 9 is wxyz.
You can return the combinations in any order. An empty string of digits has no combinations.
Examples
Example 1
- Input
- digits = "23"
- Output
- ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"]
Example 2
- Input
- digits = ""
- Output
- []
Example 3
- Input
- digits = "2"
- Output
- ["a", "b", "c"]
Constraints
0 <= digits.length <= 4- Each digit is between
2and9.