[17. Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) ### 題目描述 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. ![](https://assets.leetcode.com/uploads/2022/03/15/1200px-telephone-keypad2svg.png =50%x) ### 範例 **Example 1:** ``` Input: digits = "23" Output: ["ad","ae","af","bd","be","bf","cd","ce","cf"] ``` **Example 2:** ``` Input: digits = "" Output: [] ``` **Example 3:** ``` Input: digits = "2" Output: ["a","b","c"] ``` **Constraints**: * 0 <= `digits.length` <= 4 * `digits[i]` is a digit in the range `['2', '9']`. ### 解答 ### Reference [回到題目列表](https://hackmd.io/@Marsgoat/leetcode_every_day)