CS 101
What does CPU stand for?
Central Processing Unit
You're waiting in line at Chipotle. What data structure does that represent?
Queue — first in, first out
What does it mean when an algorithm is O(n)?
Its runtime grows linearly — double the input, double the time
What does HTML stand for?
HyperText Markup Language
You hit "undo" in VSCode. What data structure makes that possible?
Stack — last action is the first to undo
You're searching for a name in a sorted list of 1 million people. Why is binary search way better than checking one by one?
Binary search cuts the list in half each time — O(log n) vs O(n)
What's the difference between RAM and a hard drive?
RAM is temporary/fast, hard drive is permanent storage
Why would you use a dictionary/hashmap over a regular list?
Faster lookups on average — O(1) vs O(n) — because you search by key directly instead of scanning through every element
What's the difference between recursion and a regular loop?
Recursion = function calls itself, loop = repeats a block. Recursion is cleaner for problems that naturally split into smaller versions of themselves
What does it mean for a function to "return" something?
It sends a value back to whoever called it
You're building a feature that checks if a user's code has matching brackets. What data structure do you reach for and why?
Stack — push open brackets, pop when you see a closing one
Why do we sort data before doing certain operations on it?
Makes searching faster — binary search, merging, and comparisons all rely on order
What's the difference between a compiled language and an interpreted language?
Compiled = translated all at once before running, interpreted = translated line by line as it runs
Your app is slow. Someone says "maybe it's the data structure you're using." What does that actually mean?
Different structures have different time complexities — wrong choice = slower reads, writes, or searches)
What's the difference between breadth first search and depth first search?
BFS = explore level by level, good for shortest path. DFS = go as deep as possible first, good for exploring all possibilities