Longest Repeating Character Replacement

Sliding window · Keep a window valid under a budget · Stretch · about 30 min

Why it matters

This sharpens the skill of writing and maintaining a window invariant.

How it connects

The window now permits repeats, but only while the replacement budget can repair them.

Try first

How many replacements are needed to make a window all one character?

Interview cue

The valid-window condition is exactly replacementsNeeded ≤ k.