Ace Looping: For vs While—Master Iteration Patterns for Coding Interviews | MockRounds

Loop mastery separates passable solutions from efficient, bug-free interview code.

In this short session, you’ll tackle rapid-fire loop challenges over arrays and collections, watch answers revealed after each prompt, and pick up concise tips on choosing between for, while, and for-each styles.

Quiz link:https://mockrounds.com/prog_fundament...

Choose the loop by what you know: use for when bounds are known, while for sentinel/stream conditions, and for-each when you don’t need the index.

Guard against off-by-one errors: iterate 0 to n-1; prefer strict “less than” bounds; consider caching size or length if accessed repeatedly.

Don’t mutate a collection while iterating unless using a safe iterator pattern; otherwise stage changes or iterate over a snapshot.

Favor early exits (break or return) once the goal is reached to cut average time; keep a clear loop invariant to reason about correctness.

Before nesting loops, justify O(n²); consider two-pointer, sliding window, hashing, or prefix sum techniques to reduce complexity.

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