leetcode

Letter Combinations of a Phone Number

Letter Combinations of a Phone Number

Binary Search Version - 36ms

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
class Solution:
    def letterCombinations(self, digits):
        """
        :type digits: str
        :rtype: List[str]
        """
        if not digits: return []
        res = ['']
        nums =  list(digits)
        d = {'2': ['a', 'b', 'c'], '3': ['d', 'e', 'f'], '4': ['g', 'h', 'i'], '5': ['j', 'k', 'l'], '6': ['m', 'n', 'o'
], '7': ['p', 'q', 'r', 's'], '8': ['t', 'u', 'v'], '9': ['w', 'x', 'y', 'z']}
        for n in digits:
            lst = d[n]
            new_res = []
            for char in lst:
                for string in res:
                    new_res.append(string + char)
            res = new_res
        return res

test code

1
2
3
4
In [347]: s = Solution(); t = s.letterCombinations('23')
In [349]: print(t)
['ad', 'bd', 'cd', 'ae', 'be', 'ce', 'af', 'bf', 'cf']

leet code