Letter Combinations of a Phone Number
Problem Given a string of digits 2–9, return all possible letter combinations the number could represent on a telephone keypad, in any order.
Input / Output
- Input: string digits.
- Output: list of all letter combinations (empty list for empty input).
Constraints
- 0 <= |digits| <= 4 in the classic setting; output size is up to 4^n — exponential by nature.
Example
- "23" → ["ad","ae","af","bd","be","bf","cd","ce","cf"]
asked …