875. 爱吃香蕉的珂珂

二分查找

class Solution {
    public int minEatingSpeed(int[] piles, int h) {

        /**
         * Arrays.stream(arr).max().getAsInt()方法获取数组最大值
         */
        int minSpeed = 1;
        int maxSpeed = Arrays.stream(piles).max().getAsInt();

        /**
         * 使用二分查找法，最小速度肯定在[minSpeed, maxSpeed]之间，其花费的时间为小于等于h的最大值
         */
        while (minSpeed < maxSpeed) {

            int speed = minSpeed + (maxSpeed - minSpeed) / 2;

            if (time(speed, piles) > h){

                minSpeed = speed + 1;
            }
            else {
                maxSpeed = speed;
            }
        }

        return minSpeed;
    }

    public int time(int speed, int[] piles){

        int res = 0;

        for (int i = 0; i < piles.length; i++) {

            /**
             * 时间需要向上取整，同时要变成double型，防止精度遗失
             */
            res += Math.ceil(piles[i] / 1.0 / speed);
        }

        return res;
    }
}

/**
 * 时间复杂度 O(nlogn)
 * 空间复杂度 O(1)
 */

https://leetcode-cn.com/problems/koko-eating-bananas/