Koko Eating Bananas

Write `min_eating_speed(piles, h)` returning the smallest integer speed `k` such that eating `k` bananas per hour finishes every pile within `h` hours. A pile takes `ceil(pile / k)` hours and a partial hour is still an hour. min_eating_speed([3, 6, 7, 11], 8) -> 4 The input is not sorted and sorting it would not help — the thing you binary search is the *speed*, over `[1, max(piles)]`. It works because "can finish at speed k" is monotonic: true at some k, true at every larger one. Name that property; it is the reason the technique applies.