Leetcode 17. Letter Combinations of a Phone Number

17. Letter Combinations of a Phone Number

給定一數字字串,每一數字都有其可能對應到的字母，求出此數字字串可能對應到的所有字母字串組合

如果是空字串，字母字元個別放入一空陣列res，結束後回傳res，若不為空則依序加入字典所代表的值

class Solution:
    def letterCombinations(self, digits: str) -> List[str]:         
        if digits == '':
            return []
        
        digit_chr = {'2':'abc', '3':'def', '4':'ghi', '5':'jkl', '6':'mno', '7':'pqrs', '8':'tuv', '9':'wxyz'}
        output =list(digit_chr[digits[0]]) 
        
        for digit in digits[1:]:
            temp= []
            for str1 in output:
                for str2 in list(digit_chr[digit]):
                    temp.append(str1+str2)
            output = temp
                    
        return output