Greedy Questions at Zeta: What to Expect

Greedy algorithms are a small but critical slice of Zeta’s technical interview, representing about 14% of their problem set. While 5 out of 35 questions may seem modest, these problems are often high-signal for interviewers. They test your ability to identify optimal substructure and make a series of locally optimal choices that lead to a globally optimal solution. Success here demonstrates sharp problem-solving intuition and the ability to argue for the correctness of your approach—a key skill Zeta looks for in engineering roles.

What to Expect — Types of Problems

Zeta’s greedy questions typically fall into predictable categories. You’re unlikely to encounter obscure, highly mathematical greedy proofs. Instead, expect practical problems centered on scheduling, intervals, and resource allocation.

• Interval Problems: These are classics. You might be asked to find the minimum number of rooms for meetings, the maximum number of non-overlapping intervals, or to schedule tasks to minimize idle time. The core skill is sorting intervals by their start or end time and then making a greedy traversal.
• Assignment & Partitioning: Problems where you need to assign resources (like tasks to workers) or split a sequence into segments under certain constraints (e.g., partition labels). The greedy choice often involves processing items in a specific order and assigning them based on current capacity or boundaries.
• Coin Change / Making Change: While the canonical coin change problem is dynamic programming, variations with standard denominations (like quarters, dimes, nickels) are solved greedily. Zeta may present a scenario that maps to this pattern.
• String Manipulation: Problems like reorganizing a string so no two adjacent characters are the same often use a greedy approach with a priority queue to always place the most frequent character next.

The common thread is the need to sort or prioritize your input data as a first step.

How to Prepare — Study Tips with One Code Example

Your preparation should focus on pattern recognition, not memorization. Follow these steps:

1. Master the Fundamentals: Ensure you deeply understand core greedy patterns: sorting by end time for intervals, using a max-heap for frequent elements, and the two-pointer approach for assignments.
2. Prove It to Yourself: For each problem, don’t just implement the solution. Practice verbally explaining why the greedy choice is safe. This is what interviewers want to hear.
3. Code Fluently: The implementations are usually concise. You must be able to write bug-free, efficient code quickly under pressure.

A key pattern is the "Greedy Interval Scheduling" problem: Given a list of intervals, find the maximum number of non-overlapping intervals. The optimal greedy strategy is to always pick the interval that ends the earliest, as it leaves the most room for future intervals.

def max_non_overlapping(intervals):
    # Sort intervals by their end time
    intervals.sort(key=lambda x: x[1])
    count = 0
    last_end = float('-inf')

    for start, end in intervals:
        if start >= last_end:  # No overlap
            count += 1
            last_end = end
    return count

Recommended Practice Order

Tackle problems in this order to build competence progressively:

1. Classic Foundations: Start with canonical problems like "Maximum Subarray," "Jump Game," and "Merge Intervals." These teach the basic proof of concept.
2. Core Zeta Patterns: Move to high-probability Zeta categories: "Meeting Rooms II" (interval scheduling with resources), "Task Scheduler" (greedy with heap), and "Partition Labels."
3. Variations & Edge Cases: Practice problems that twist the classics, such as "Minimum Number of Arrows to Burst Balloons" (interval scheduling with a twist on overlap) or "Gas Station."
4. Timed Mock Interviews: Finally, simulate the real interview. Pick a Zeta-tagged greedy problem and solve it aloud within 25 minutes, explaining your reasoning throughout.

Practice Greedy at Zeta