LeetCode 笔记十二 九宫格按键的字母组合

Letter Combinations of a Phone Number

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.
A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.

大概就是说，我们手机上九宫格按键从2~9分别对应着26个英文字母，我们要做的事情就是，当你按下阿拉伯数字组合时，输出这个组合可能的英文字母组合。
我们来看下他的例子：

example

Input: “23”
Output: [“ad”, “ae”, “af”, “bd”, “be”, “bf”, “cd”, “ce”, “cf”].

Code

如果写过之前的题，很显然这道题也自然而然地就会想到用字典的方式去做，以下直接贴代码:

class Solution:
    def letterCombinations(self, digits: str) -> List[str]:
        if digits == '':
            return []
        
        digitsDict = {'2':'abc', '3':'def',
                      '4':'ghi', '5':'jkl', '6':'mno',
                      '7':'pqrs', '8':'tuv', '9':'wxyz'}
        
        def wordCombine(pres, dicts, digit):
            r = []
            for p in pres:
                for l in dicts[digit]:
                    r.append(p + l)
            return r
        
        results = ['']
        for d in digits:
            results = wordCombine(results, digitsDict, d)
            
        return results

结果如下:

25 / 25 test cases passed.
Runtime: 24 ms
Memory Usage: 12.7 MB

Runtime: 24 ms, faster than 94.25% of Python3 online submissions for Letter Combinations of a Phone Number.
Memory Usage: 12.7 MB, less than 100.00% of Python3 online submissions for Letter Combinations of a Phone Number.