875. Koko Eating Bananas

[fockspaces]

use Binary search to find the minimun speed to eat

1. set boundary
2. l = 1 (we should at least eat one per hour), r = max(piles) (if we keep the speed of max amount in piles, we can finish in len(piles) hour)
3. keep updating, we want to search the most left possible one, the base case is total_hour > h, it means we eat too slow, should be more aggresive to eat

class Solution:
    def minEatingSpeed(self, piles: List[int], h: int) -> int:
        l, r = 1, max(piles)
        while l < r:
            mid = (l + r) // 2
            total_hour = 0
            for pile in piles:
                spend_hour = math.ceil(pile / mid)
                total_hour += spend_hour
            if total_hour > h:
                l = mid + 1
            else:
                r = mid
        return l