Water drops from each bucket into the container below, overflowing into the next. Once the containers are full, any range query is just two numbers apart — no re-summing, ever.
Controls
💧 PerciI pre-fill every container once. After that, any range you ask for, I answer in one subtraction.
🥾 TrekI walk the array every single time you ask. Reliable — but my legs are tired of O(n).