17. Letter Combinations of a Phone Number

Updated: 2024-03-12
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LeetCode problem

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:

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

Example 2:

Input: digits = ""
Output: []

First accepted

class Solution:
    def letterCombinations(self, digits: str) -> List[str]:
        if not digits:
            return []
        letters = ['', '', 'abc', 'def', 
                      'ghi', 'jkl', 'mno', 
                      'pqrs', 'tuv', 'wxyz']
        result = ['']
        for d in digits:
            d = int(d)
            tmp = []
            for letter in letters[d]:
                for word in result:
                    word += letter
            result = tmp
        return result