String Algorithms and Pattern Matching

String questions look approachable and hide real depth. Checking a palindrome is a two-pointer exercise; finding one substring inside another efficiently is a genuine algorithmic problem that took decades to solve well.

These lessons walk the full range. The naive search visualizer shows exactly where the wasted comparisons happen, which is the setup for KMP — and KMP only makes sense once you have watched its failure function skip the work the naive version repeats. Rabin-Karp covers the rolling-hash idea that reappears in deduplication and substring problems well outside interviews.