17. Letter Combinations of a Phone Number

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原创最新推荐文章于 2026-04-23 10:05:20 发布 430 阅读 AI 写同款· GEO 优化 ›

Matlab：Matlab 软件学习之Matlab内置的各种系统的简介、案例应用(基于Simulink模糊控制仿真/二阶瞬态震荡电路案例)之详细攻略选择左上角要编辑变量的图标，给定当前变量的论域Range，设置隶属函数类型type(八种隶属函数类型以供选择)，最后选中某个隶属度函数(选中为红色)，移动绘图区的每个隶属度函数的三个端点(竖向为权重)。(1)、首先在模糊规则编辑器左边选择一个输入变量，并选中它的一个语言值(隶属函数)，然后编辑器右边选择一个输出变量，并选中它的一个语言值(隶属函数)，然后将这种关系添加到模糊规则中。制定完成后，会形成模糊规则矩阵，系统会根据模糊输入量(如r1、r2)，经过模糊规则(如45条)，进而确定输出量(Y1、Y2)。阅读详情

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"].

Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.

do a dfs search to see all the combinations.

class Solution(object):
    def letterCombinations(self, digits):
        """
        :type digits: str
        :rtype: List[str]
        """
        NUMBER_HASH={'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']
             }
        digit_length = len(digits)
        def dfs(number_length, string, result):
            if number_length == digit_length:
                result.append(string)
                return
            for letter in NUMBER_HASH[digits[number_length]]:
                dfs(number_length + 1, string + letter, result)
        result = []
        if len(digits) == 0:
            return result
        dfs(0, '', result)
        return result