Koko Eating Bananas

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Intuition

Binary search on eating speed k. At speed k, hours needed = sum(ceil(pile/k)). Find minimum k where hours <= H.

Algorithm

1lo=1, hi=max(piles).
2Feasibility(k): sum(ceil(pile/k)) <= H.
3Return minimum feasible k.

Common Pitfalls

•ceil(pile/k) = (pile+k-1)/k in integer arithmetic. Binary search on speed, not on hours.

Koko Eating Bananas.java

Java

// Approach: Binary search on eating speed k. For each k, check if Koko finishes all piles in H hours.
// Time: O(n log(max_pile)) Space: O(1)
import java.util.*;

class Solution {
    public int kokoEat(int[] arr, int k) {
        Arrays.sort(arr);
        int ans = -1;
        int low = 1;
        int high = (int) 1e9;
        while (low <= high) {
            int mid = low + (high - low) / 2;
            if (ispossible(arr, mid) <= k) {
                ans = mid;
                high = mid - 1;
            } else
                low = mid + 1;
        }

        return ans;
    }

    private int ispossible(int[] arr, int mid) {
        int ans = 0;
        for (int i = 0; i < arr.length; i++) {
            int cnt = arr[i] / mid;
            if (arr[i] % mid != 0)
                cnt++;

            ans += cnt;
        }
        
        return ans;
    }
}

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