LinkedIn 高频算法题：手机号数字映射单词（Phone Keypad Word Mapping）面试真题解析

Given the standard mapping from English letters to digits on a phone keypad:

(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)

Write a program that outputs all words that can be formed from any n-digit phone number
from the list of given KNOWN_WORDS, considering the mapping mentioned above.

KNOWN_WORDS = ['careers', 'linkedin', 'hiring', 'interview', 'linkedgo']

phoneNumber: 2273377  
Output: ['careers']

phoneNumber: 54653346  
Output: ['linkedin', 'linkedgo']

这是一道典型的 手机号 → 字母映射 → 单词过滤 的面试题，核心不在暴力枚举，而在于如何高效地把 单词反向映射成数字模式。面试官重点观察候选人是否能快速识别优化方向、正确分析时间复杂度，并在解释过程中保持逻辑清晰。

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