Koko Eating Bananas - Code

Here is the implementation:

function minEatingSpeed(piles, h):
    low = 1
    high = max(piles)

    while low < high:
        mid = low + (high - low) / 2
        if canFinish(piles, mid, h):
            high = mid
        else:
            low = mid + 1

    return low

function canFinish(piles, k, h):
    hours = 0
    for pile in piles:
        hours = hours + ceil(pile / k)
    return hours <= h

Pattern recognition: Whenever you see "minimum $X$ such that condition is satisfied" or "maximum $X$ such that condition is satisfied," think binary search on the answer.

The answer is $low$ after the loop. Since we use high = mid when valid, we find the smallest valid answer.