cpp-flashcards/org/study_deck_02/dsa/backtracking/0017-letter-combinations-of-a-phone-number.org

#+ANKI_DECK: study_deck_02
* TODO 0017. Letter Combinations of a Phone Number :medium:
:PROPERTIES:
:NEETCODE: [[file:../../roadmap.org::*0017. Letter Combinations of a Phone Number][0017. Letter Combinations of a Phone Number]]
:END:

Given a string containing digits from ~2-9~ inclusive, return all possible letter combinations that the number could represent. Return the answer in *any order*.

A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.

*Example 1:*


#+begin_src
Input: digits = "23"
Output: ["ad","ae","af","bd","be","bf","cd","ce","cf"]
#+end_src


*Example 2:*


#+begin_src
Input: digits = "2"
Output: ["a","b","c"]
#+end_src


*Constraints:*

 - ~1 <= digits.length <= 4~

 - ~digits[i]~ is a digit in the range ~['2', '9']~.

** TODO Approach
Write your approach here.

** TODO Python
#+begin_src python
class Solution:
    def letterCombinations(self, digits: str) -> List[str]:
#+end_src

** TODO C++
#+begin_src cpp
class Solution {
public:
    vector<string> letterCombinations(string digits) {
        
    }
};
#+end_src