[LintCode] 183. Wood Cut

 

Given n pieces of wood with length L[i] (integer array). Cut them into small pieces to guarantee you could have equal or more than k pieces with the same length. What is the longest length you can get from the n pieces of wood? Given L & k, return the maximum length of the small pieces.

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The unit of length is centimeter.The length of the woods are all positive integers,you couldn't cut wood into float length.If you couldn't get >= k pieces, return 0.

Example 1

Input:
L = [232, 124, 456]
k = 7
Output: 114
Explanation: We can cut it into 7 pieces if any piece is 114 long, however we can't cut it into 7 pieces if any piece is 115 long.
And for the 124 logs, the excess can be discarded and not used in its entirety.

Example 2

Input:
L = [1, 2, 3]
k = 7
Output: 0
Explanation: It is obvious we can't make it.

Challenge

O(n log Len), where Len is the longest length of the wood.

木材加工。

有一些原木，现在想把这些木头切割成一些长度相同的小段木头，需要得到的小段的数目至少为 k。给定L和k，你需要计算能够得到的小段木头的最大长度。

这道题的思路是二分，而且是在答案上二分。对于所有的木头而言，切割的长度的下界是1，上界是最长的那个木材的长度。在这个范围内进行二分，用每次二分得到的潜在的mid长度再去计算到底能切割成几个小段。

时间O(nlogn)

空间O(1)

Java实现

 1 public class Solution {
 2     /**
 3      * @param l: Given n pieces of wood with length L[i]
 4      * @param k: An integer
 5      * @return: The maximum length of the small pieces
 6      */
 7     public int woodCut(int[] logs, int k) {
 8         // write your code here
 9         int len = logs.length;
10         long sum = 0;
11         int max = 0;
12         for (int log : logs) {
13             max = Math.max(max, log);
14             sum += log;
15         }
16         // corner case
17         if (sum < k) {
18             return 0;
19         }
20 
21         // normal case
22         int left = 1;
23         int right = max;
24         while (left + 1 < right) {
25             int mid = left + (right - left) / 2;
26             if (isValid(logs, k, mid)) {
27                 left = mid;
28             } else {
29                 right = mid;
30             }
31         }
32         if (isValid(logs, k, right)) {
33             return right;
34         }
35         return left;
36     }
37 
38     private boolean isValid(int[] logs, int k, int mid) {
39         int count = 0;
40         for (int log : logs) {
41             count += log / mid;
42         }
43         if (count >= k) {
44             return true;
45         }
46         return false;
47     }
48 }

 

LeetCode 题目总结

标签：Cut,return,logs,int,mid,pieces,183,length,Wood
来源： https://www.cnblogs.com/cnoodle/p/16329100.html