Day 1/365: Big O Notation -- DSA & System Design

365 Day DSA & System Design Challenge

Day 1 had to start with Big O notation because it sets the performance language for everything that comes next.

What I wanted clear today:

• Big O is about growth, not exact runtime on one machine
• O is an upper bound, Omega is a lower bound, and Theta is the tight bound
• one loop over n items usually means linear work, while nested loops are the first serious warning sign
• asymptotic analysis matters because an algorithm that feels fine on tiny input can fail badly at larger scale
• later DSA topics only make sense once I can ask which operation dominates the runtime

That made Day 1 feel much more practical than memorizing notation as isolated theory. It turned complexity into a way to read code and compare solutions before scale makes the wrong choice painful.

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Day 1/365 of the 365 Day DSA & System Design Challenge.