Solve stock profit and vertical tree traversal
Company: Uber
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
You have a 60-minute coding interview with two algorithm questions:
1) **Max profit from one stock trade**
- Input: an integer array `prices`, where `prices[i]` is the stock price on day `i`.
- Task: Choose **one** day to buy and a **later** day to sell to maximize profit. Return the maximum profit; if no profitable trade is possible, return `0`.
2) **Vertical traversal of a binary tree**
- Input: the root of a binary tree.
- Define coordinates: root at `(row=0, col=0)`, left child `(row+1, col-1)`, right child `(row+1, col+1)`.
- Task: Return the nodes grouped by vertical columns from leftmost `col` to rightmost.
- Within each column, order nodes by `row` ascending (top to bottom).
- If multiple nodes share the same `(row, col)`, order those nodes by their value ascending.
- Output: a list of lists of node values following this ordering.
Quick Answer: Assesses proficiency in array processing and binary tree traversal algorithms—specifically single-pass analysis of time-series data and coordinate-based vertical ordering of tree nodes; Category: Coding & Algorithms; Level of abstraction: implementation-level algorithmic coding.