LeetCode: 875. Koko Eating Bananas

题目描述

Koko loves to eat bananas. There are N piles of bananas, the i-th pile has piles[i] bananas. The guards have gone and will come back in H hours.
Koko can decide her bananas-per-hour eating speed of K. Each hour, she chooses some pile of bananas, and eats K bananas from that pile. If the pile has less than K bananas, she eats all of them instead, and won’t eat any more bananas during this hour.

Koko likes to eat slowly, but still wants to finish eating all the bananas before the guards come back.
Return the minimum integer K such that she can eat all the bananas within H hours.

Example 1:

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

Example 2:

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

Example 3:

Input: piles = [30,11,23,4,20], H = 6
Output: 23

Note:

1 <= piles.length <= 10^4 piles.length <= H <= 10^9 1 <= piles[i] <= 10^9

解题思路

K 可能的最小值实际橡胶总数除以最大小时数。从该值开始，枚举 K 可能的结果，直到满足要求的结果出现为止。

AC 代码

class Solution {
public:
    int minEatingSpeed(vector<int>& piles, int H) {
        long long int bananas = 0;
        for(int bnum : piles)
        {
            bananas += bnum;
        }

        int kexp = (bananas+H-1)/H;

        while(true)
        {
            int t = 0;
            for(int i = 0; i < piles.size(); ++i)
            {
                t += (piles[i]/kexp + (piles[i]%kexp != 0));
            }
            if(t <= H) 
            {
                return kexp;
            }
            ++kexp;

            if(kexp >= bananas)
            {
                return -1;
            }
        }
    }
};