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.

SRE实战 互联网时代守护先锋，助力企业售后服务体系运筹帷幄！一键直达领取阿里云限量特价优惠。

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

 Idea 1. Binary search, similar to Capacity To Ship Packages Within D Days LT1011, search space: (ceiling(sum(piles)/h), max(piles))

ceiling(sum(piles)/h) = (sum(piles)-1)/h + 1

也可以免去一次遍历数组，直接设置search space (1, 10^9)

Time complexity: O(nlogw), n is the size of piles, w is the maximum of piles.

Space complexity: O(1)

 1 class Solution {
 2     private int checkHours(int[] piles, int speed) {
 3         int hours = 0;
 4         for(int pile: piles) {
 5             int hour = (pile-1)/speed + 1;
 6             //int hour = ((pile%speed == 0) ? pile/speed : pile/speed + 1);
 7             hours += hour;
 8         }
 9         return hours;
10     }
11     public int minEatingSpeed(int[] piles, int H) {
12         int min = 1, max = 0;
13         for(int pile: piles) {
14             max = Math.max(max, pile);
15         }
16         
17         while(min < max) {
18             int mid = min + (max - min)/2;
19             int hours = checkHours(piles, mid);
20             if(hours <= H) {
21                 max = mid;
22             }
23             else {
24                 min = mid + 1;
25             }
26         }
27         
28         return min;
29     }
30 }

 

扫码关注我们
微信号：SRE实战
拒绝背锅 运筹帷幄