题目如下:
17. Letter Combinations of a Phone Number
Given a string containing digits from 2-9
inclusive, 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. Note that 1 does not map to any letters.
Example:
Input: "23" Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.
代码如下:
class Solution: def letterCombinations(self, digits): """ :type digits: str :rtype: List[str] """ zmb={'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']} def get_ans(l,i,digits,ans,tem): if(i<l): for k in zmb[digits[i]]: get_ans(l,i+1,digits,ans,tem+k) elif(l==i): if (tem!=""): ans.append(tem) return ans=[] l=len(digits) i=0 tem="" get_ans(l,i,digits,ans,tem) return ans
分析如下:
先创建一个字典,将每一个数字字符作为key,对应的字母列表作为value。
运用函数递归,L为数字字符的长度,若进行的递归次数大于长度,则将得到的字符串append到ans列表里。
最终通过递归得到答案。
结果如下: