[LeetCode][python3]0017. Letter Combinations of a Phone Number

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N2I -2020.04.02

1. My first try

  1. class Solution:
  2.     def letterCombinations(self, digits: str) -> List[str]:      
  3.         if not digits:
  4.             return []
  5.         dic={'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']}
  6.         ans=dic[digits[0]]
  7.         for d in digits[1:]:
  8.             ans=self.listxlist(ans,dic[d])       
  9.         return ans
  10.         
  11.     def listxlist(self,a,b):
  12.         #print("hello")
  13.         #print(a,b)
  14.         combine=[]
  15.         for item_a in a:
  16.             for item_b in b:
  17.                 combine.append(item_a+item_b)
  18.         return combine

Explanation:

The Solution use a small custom function listxlist to finish the work.