最有效的材料分配有序java编程问题：
这是一个编程问题，我根本无法处理。这是一个面试问题，所以需要在10-15分钟内解决。
一家公司希望自动订购三种尺寸的木材 董事会成为最具成本效益的订单（更长的董事会更少 昂贵）。木材公司提供的木材出售 16'，12'和8'板。板越长越便宜。
订单是针对7'，6'和5'板的倍数单位。所以 你可以从一个16'中获得两个7'板，或者从5'中获得两个7'板 16'）等。如果您只需要两个5'板，您可以订购 单身12'，而不是16'。
编写一个算法，该算法将接收混合板数量的订单 三种类型并返回效率最高（性价比高） 订购（最多）三种可用尺寸。
我不禁想到改变最佳造币的问题，但与此相比，这相对简单。似乎有项目频率的元素，但我看不出如何分配最佳顺序。
我认为这是一个两步过程，第一步是将频率记录在地图中，例如6 x 7页脚，5 x 6页脚等。频率图按值排序，这就是我卡住的地方。
只是为了澄清：更大的电路板更便宜，应尽可能先使用。
我会继续关注这一点，但如果有人有想法，我们将不胜感激。
答案 0 :(得分：0)
package max.test.com;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
/*
* Board Cutter algorithm based on John T Erickson's
* code found at http://pastebin.com/1XPiBD20
*
* I can't take credit for it - I just rendered it to Java
*
* Max Tomlinson
*
*/
public class BoardCutter
{
static List<Double> boards;
static List<Double> lengthsNeeded;
static double cutWidth = Double.NaN;
static double totalBoardLength;
static int lengthsNeededLeft = 0;
static List<String> instructions = new ArrayList<String>();
static List<String> summary = new ArrayList<String>();
public static void main(String[] args)
{
double[] tmp = new double[] { 48, 48, 48, 48, 48, 48 };
boards = new ArrayList<Double>();
for (int i = 0; i < tmp.length; i++)
{
boards.add(tmp[i]);
totalBoardLength += tmp[i];
}
lengthsNeeded = new ArrayList<Double>();
tmp = new double[] { 36.75, 36.5, 36.5, 26.25, 26.125, 22.5, 21, 20.5,
14.5, 9.25, 9, 6.5, 4 };
for (int i = 0; i < tmp.length; i++)
{
lengthsNeeded.add(tmp[i]);
}
cutWidth = 0.125;
Collections.sort(lengthsNeeded);
Collections.reverse(lengthsNeeded); //sorted high to low - biggest cuts first
lengthsNeededLeft = lengthsNeeded.size();
writeLine("Boards: ");
double boardSum = 0;
Iterator<Double> itd = boards.iterator();
while (itd.hasNext())
{
double board = itd.next();
writeLine("" + board);
boardSum += board;
}
writeLine("Total: " + boardSum);
writeLine("Lengths Needed:");
double lengthsNeededSum = 0;
itd = lengthsNeeded.iterator();
while (itd.hasNext())
{
double ln = itd.next();
writeLine("" + ln);
lengthsNeededSum += ln;
}
writeLine("Total: " + lengthsNeededSum);
tryCut();
Collections.reverse(instructions);
for (int i = 0; i < instructions.size(); i++)
writeLine("Cut " + (i + 1) + ": " + instructions.get(i));
for (int i = 0; i < summary.size(); i++)
writeLine(summary.get(i));
}
/*
* recursive cutting method
*/
static boolean tryCut()
{
//last case, then exit
if (lengthsNeededLeft == 0)
{
double boardLengthRemaining = 0;
Iterator<Double> it = boards.iterator();
while (it.hasNext())
{ // sum
double board = it.next();
if (!Double.isNaN(board))
boardLengthRemaining += board;
}
summary.add("Boards Remaining: ");
for (int j = 0; j < boards.size(); j++)
{
if (boards.get(j).equals(Double.NaN)) continue;
summary.add(" Board " + j + ": " + boards.get(j));
}
summary.add("Total Remaining " + boardLengthRemaining
+ " efficiency "
+ (100 * (1 - (boardLengthRemaining) / totalBoardLength)));
return true;
}
//normal, recursive case
//loop for all lengths needed
for (int i = 0; i < lengthsNeeded.size(); i++)
{
double lengthNeeded = lengthsNeeded.get(i);
if (Double.isNaN(lengthNeeded)) continue; //isNaN = 'done'
for (int j = 0; j < boards.size(); j++)
{
double board = boards.get(j);
if ( Double.isNaN(board)) continue; //isNaN = 'in use'
double boardRemaining = board - lengthNeeded - cutWidth;
if (boardRemaining >= 0.0)
{
lengthsNeeded.set(i, Double.NaN); //set this length needed to 'done'
lengthsNeededLeft--;
boards.set(j, Double.NaN); //set board to used
boards.add(0, boardRemaining); //add new cut board remainder to front of available boards for possible reuse
int newBoardIndex = boards.size() - 1; //adjust size
//recursive call
if (tryCut())
{
instructions.add("Cut board " + (j + 1) + " of length " + board
+ " to size: " + lengthNeeded
+ " (leaving board " + (newBoardIndex + 1) + " of length "
+ boardRemaining + ")");
return true;
}
boards.remove(boards.size() - 1);
lengthsNeeded.set(i, lengthNeeded);
lengthsNeededLeft++;
boards.set(j, board);
}
}
}
// all boards are too short
return false;
}
static void writeLine(String s)
{
System.out.println(s);
}
}
//output
/*
Boards:
48.0
48.0
48.0
48.0
48.0
48.0
Total: 288.0
Lengths Needed:
36.75
36.5
36.5
26.25
26.125
22.5
21.0
20.5
14.5
9.25
9.0
6.5
4.0
Total: 269.375
Cut 1: Cut board 1 of length 48.0 to size: 36.75 (leaving board 7 of length 11.125)
Cut 2: Cut board 2 of length 48.0 to size: 36.5 (leaving board 8 of length 11.375)
Cut 3: Cut board 3 of length 48.0 to size: 36.5 (leaving board 9 of length 11.375)
Cut 4: Cut board 4 of length 48.0 to size: 26.25 (leaving board 10 of length 21.625)
Cut 5: Cut board 5 of length 48.0 to size: 26.125 (leaving board 11 of length 21.75)
Cut 6: Cut board 6 of length 48.0 to size: 22.5 (leaving board 12 of length 25.375)
Cut 7: Cut board 10 of length 21.625 to size: 21.0 (leaving board 13 of length 0.5)
Cut 8: Cut board 11 of length 21.75 to size: 20.5 (leaving board 14 of length 1.125)
Cut 9: Cut board 12 of length 25.375 to size: 14.5 (leaving board 15 of length 10.75)
Cut 10: Cut board 7 of length 11.125 to size: 9.25 (leaving board 16 of length 1.75)
Cut 11: Cut board 8 of length 11.375 to size: 9.0 (leaving board 17 of length 2.25)
Cut 12: Cut board 9 of length 11.375 to size: 6.5 (leaving board 18 of length 4.75)
Cut 13: Cut board 15 of length 10.75 to size: 4.0 (leaving board 19 of length 6.625)
Boards Remaining:
Board 12: 0.5
Board 13: 1.125
Board 15: 1.75
Board 16: 2.25
Board 17: 4.75
Board 18: 6.625
Total Remaining 17.0 efficiency 94.09722222222221
*/