Given a digit string, 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.
Input:Digit string "23" Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
题意：输入一个数字字符串，返回每个数字键之间，所对应字母的所有组合
思路：每遍历到一个数字，把这个数字中的所有字符和原列表中的所有字符串相加
class Solution(object): def letterCombinations(self, digits): """ :type digits: str :rtype: List[str] """ if digits==‘‘: return [] flag={‘1‘:[‘*‘], ‘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‘], ‘0‘:[‘ ‘] } t = flag[digits[0]] res = t for c in digits[1:]: t = flag[c] res = [i+j for i in res for j in t] return res
【LeetCode】17. Letter Combinations of a Phone Number
原文：http://www.cnblogs.com/fcyworld/p/6213346.html