[leetcode] 17. Letter Combinations of a Phone Number
阿新 • • 發佈:2022-03-29
題目
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 digit 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: []
Example 3:
Input: digits = "2"
Output: ["a","b","c"]
Constraints:
0 <= digits.length <= 4
-
digits[i]
is a digit in the range['2', '9']
.
思路
序列全排列的變種。
程式碼
python版本:
class Solution: def letterCombinations(self, digits: str) -> List[str]: num_map = { '1': '', '2': 'abc', '3': 'def', '4': 'ghi', '5': 'jkl', '6': 'mno', '7': 'pqrs', '8': 'tuv', '9': 'wxyz', } if not digits: return [] res = [''] for num in digits: res = [r+letter for r in res for letter in num_map[num]] return res