
How to Study for Data Structures and Algorithms in 2025
You ever stare at a recursion problem at 2 a.m. wondering if maybe business school wasn’t such a bad idea? Yeah, same, been there done that.
I’m Jorde, an senior engineer who took DSA twice (Java and C++) and learned the hard way what works and what doesn’t.
DSA is the easiest class to cheat through but the hardest one to fake in an interview.
You can ChatGPT your homework, but you can’t fake reversing a linked list in front of a Google engineer (Or in my case solve an LRU cache problem in an OO interview).
Why Data Structures and Algorithms Hits Different
Most CS classes reward memorization. DSA rewards pattern recognition.
You can’t memorize 1,500 LeetCode problems(at least I can't) but you can learn to spot a pattern when you see one.
Think of it like learning an instrument: you don’t get better by reading music theory, you get better by playing the thing.
Reading about binary trees won’t make you good at them.
Writing them, breaking them, fixing them, that’s where it clicks. Albeit painful as the complexity of the problem start sliding in through different constraints.
5 Mistakes I Made (So You Don’t Have To)
1. Overcomplicating the Basics
I used to freeze up on arrays and pointers, thinking I had to master them before moving on.
You learn fundamentals by solving problems, not before. Start small. You’ll get comfortable by doing, not by rereading slides.
2. Trying to Trace Recursion in My Head
I’d mentally follow every call stack until my brain melted.
Stop proving recursion works, it does. Focus on:
- Base case: when does it stop?
- One step: what happens in this call?
- Trust: if it works for small input, it’ll work for big ones.
3. Solving Everything in My Head
I’d solve the problem mentally, then bomb the code.
Use a whiteboard or paper. Draw arrays. Trace pointers.
Logic becomes real when you see it.
4. Ignoring Edge Cases
I used to solve only the happy path. What a rookie move. Edge cases are king. Every problem → run through this checklist:
- Empty input (
[]
,null
) - Single element
- Duplicates
- Not found
- Out of bounds
5. Starting With Java/C++ Instead of Python
I spent more time debugging syntax than learning logic. Learn DSA in Python first. The benefits? Less boilerplate, fewer headaches, faster results. You can always switch languages later. Even today with most of my Go and Node experience I prefer python for interviewing.
The Only Patterns You’ll Ever Need
There aren’t thousands of unique problems. There are a handful of core patterns that keep repeating.
Two Pointers
Use two indices to traverse arrays/lists. When to use:
Find two numbers that sum to target or remove duplicates in-place. Usually O(n) time, O(1) space.
Sliding Window
A moving window that tracks properties as it slides. When to use: Longest substring without repeating characters, max sum subarray.
Fast & Slow Pointers
Two pointers, different speeds.
When to use: cycle detection, finding the middle node.
BFS / DFS
Breadth-first: level by level (queue).
Depth-first: go deep first (stack or recursion).
When to use: trees, graphs, shortest paths, exploring all possibilities.
Dynamic Programming
The final boss.
Break a problem into overlapping subproblems, reuse results.
When to use: any “maximum,” “minimum,” “count ways,” or “longest/shortest” phrasing.
How to practice
Every time you solve a problem:
- Understand (5 min): restate it, list inputs/outputs, write examples + edge cases.
- Plan (10 min): draw it, pick the pattern, walk through.
- Code (15 min): handle base cases first.
- Test (5 min): check examples + weird edge cases.
- Optimize (5 min): time/space tradeoffs.
Spaced repetition wins.
Solve today → again tomorrow → again in 3 days → again in a week.
One-and-done doesn’t build muscle memory.
Tools That Actually Help
- LeetCode - Standard practice set. Free is enough.
- NeetCode - 150 – Covers every key pattern without overwhelm.
- Digestly - Turn your DSA lectures into digestible chunks. Auto-flashcards. No rewinding nightmares.
- Visualgo - Animations for sorting, trees, graphs.
- Python Tutor - Step-by-step code visualization for recursion and pointers.
The Secret
DSA doesn’t reward talent, it rewards reps.
The person who solves 100 problems with understanding will always beat the one who brute-forces 500 mindlessly.
So when you see a new problem, ask:
What pattern is this? Have I seen something like it before?
Start small. Two easy LeetCode problems. One cup of coffee. One hour. (10 minute of the Wim Hof is optional). That’s all it takes to build momentum.
DSA isn’t about being smart.
It’s about showing up, one pattern at a time, until your brain starts seeing solutions before your fingers hit the keyboard. You’ll thank yourself later. You got this!
Ready to master DSA? Start with Digestly and turn those confusing lectures into clear, actionable study guides.