Day 5/365: Common Complexity Classes -- DSA & System Design

365 Day DSA & System Design Challenge

Day 5 was about making the common complexity ranking feel practical.

What I wanted clear today:

• O(1), O(log n), O(n), O(n log n), O(n^2), O(2^n), and O(n!) are not just labels, they are a ladder of growth
• O(1), O(log n), and O(n) are the first classes I hope to see, while O(n log n) is often still a strong result
• O(n^2) deserves immediate scrutiny because a better structure may exist
• O(2^n) and O(n!) only make sense when exhaustive search is genuinely required
• input constraints are what turn the ranking into a real decision tool

The biggest shift was treating the classes as a way to reject weak approaches early instead of memorizing an ordering chart.

That made Day 5 much more practical than pure theory. It turned the growth ladder into a way to judge which solutions can actually survive the problem in front of me.

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Day 5/365 of the 365 Day DSA & System Design Challenge.