Letter Combinations of a Phone Number

A parcel locker is opened with a word, but its keypad is the old telephone kind: every key from 2 to 9 carries a small group of lowercase letters, and the keys 0 and 1 carry none.

2 -> a b c      6 -> m n o
3 -> d e f      7 -> p q r s
4 -> g h i      8 -> t u v
5 -> j k l      9 -> w x y z

A courier watched a customer press the keys but could not see which letter on each key was intended. Given the pressed sequence as a string code, list every word that could have been meant, taking exactly one letter from the group of each key, in the order the keys were pressed.

You may list the words in whatever order you like. When code is empty nothing was pressed, so the answer is an empty list.

Examples

Constraints

• 0 <= code.length <= 4
• Every character of code is a digit from '2' through '9'.

The groups you return, and the values inside each group, may be in any order.

The signature

The editor starts with this. It matches the parent problem's shape, so a solution that works here works on a standard judge unchanged.

def keypad_spellings(code: str) -> list[str]:

public List<String> keypadSpellings(String code)