Binary Search - Koko Eating Bananas

Koko loves to eat bananas. There are n piles of bananas, the i-th pile has piles[i] bananas. Find the minimum eating speed k such that Koko can eat all bananas within h hours.

Input: piles=[3,6,7,11], h=8 → Output: 4

Input: piles=[30,11,23,4,20], h=5 → Output: 30

Binary search on the answer: search speed k in range [1, max(piles)]. For a given k, compute hours needed = sum(ceil(pile/k)). If hours <= h, try smaller k.

lo=1, hi=max(piles).
For each mid speed, compute total hours needed.
If hours <= h: possible, try smaller (hi=mid).
Else: too slow, increase speed (lo=mid+1).

class Solution { public int minEatingSpeed(int[] piles, int h) { int lo = 1, hi = 0; for (int p : piles) hi = Math.max(hi, p); while (lo < hi) { int mid = lo + (hi - lo) / 2; long hours = 0; for (int p : piles) hours += (p + mid - 1) / mid; if (hours <= h) hi = mid; else lo = mid + 1; } return lo; } }

Time Complexity: O(N log M) where M=max pile
Space Complexity: O(1)