Find largest subset sharing a common digit
Company: Google
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
You are given a list of **two-digit integers** (each from `10` to `99`, inclusive). You want to select as many numbers as possible **in one selection** such that:
- There exists a digit `d` (0–9) where **every selected number contains digit `d` in at least one position** (tens or ones).
For example, from `[11, 21, 31, 41, 16, 17, 18, 34, 57]`, you can select `11, 21, 31, 41, 16, 17, 18` (7 numbers) because they all contain digit `1`.
Return the **maximum possible size** of such a selection.
### Input
- An integer array `nums` of length `n`, where each `nums[i]` is a two-digit integer (`10`–`99`).
### Output
- An integer: the maximum number of elements you can select.
Quick Answer: This question evaluates understanding of digit-level properties within arrays and the ability to reason about selection size under explicit constraints, involving combinatorial and counting concepts.
Given two-digit integers, return the largest number of elements that all contain one common digit.
Constraints
- Numbers are two-digit integers in normal inputs
Examples
Input: ([11, 21, 31, 41, 16, 17, 18, 34, 57],)
Expected Output: 7
Input: ([23, 35, 30, 19],)
Expected Output: 3
Hints
- Count how many numbers contain each digit, counting a number once per digit even if repeated.