017 Letter Combinations of a Phone Number.py

class Solution:
    def letterCombinations(self, digits):
        """
        :type digits: str
        :rtype: List[str]
        """
        map={
            '2': 'abc',
            '3': 'def',
            '4': 'ghi',
            '5': 'jkl',
            '6': 'mno',
            '7': 'pqrs',
            '8': 'tuv',
            '9': 'wxyz'
        }
        if len(digits) == 0: return []
        print(digits[:-1])
        print(digits[-1])
        return [a+b for a in self.letterCombinations(digits[:-1])
                    for b in self.letterCombinations(digits[-1])] or list(map[digits])

a=Solution()
b=a.letterCombinations('23')
print(b)