The Data Engineer’s Leetcode Algorithm Cheat Sheet (2025)

15 Python patterns that show up in every FAANG data engineering interview — with real examples and when to use each

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Oct 8, 2025

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Data Engineers need algorithms, but we need them in a different context. We’re not building compilers or game engines. We’re processing streams, detecting anomalies, deduplicating records, and optimizing queries. Different domain, same foundational patterns.

So I sat down and compiled this cheat sheet. These are the 15 algorithmic patterns that keep showing up, with real data engineering contexts for each.

No fluff. Just templates, examples, and LeetCode problems to drill.

Pattern #1: Sliding Window

When to Use: Processing streams, finding patterns in time windows, analyzing logs within time ranges

The Template:

def sliding_window(arr):
    left = 0
    for right in range(len(arr))…