Subsets / Combinations
LC #17Medium
Letter Combinations of a Phone Number
Subsets / Combinations
AmazonGoogleMetaBloombergProblem
Return all possible letter combinations that a phone number could represent.
stringbacktrackinghash-map
Constraints
- ›0 ≤ digits.length ≤ 4
- ›digits[i] is in ['2','9']
Example
Input
digits = "23"Output
["ad","ae","af","bd","be","bf","cd","ce","cf"]Why
2→abc, 3→def. All combinations: 3×3 = 9