编辑代码

import java.util.*;

public class Backpack {
    public static LinkedList<GreedyItem> packBean(int packCapacity, GreedyItem[] items) {
        LinkedList<GreedyItem> beans = new LinkedList<GreedyItem>(); // 记录需要装包的豆子

        //按照单价从高到低进行排序
        Arrays.sort(items, new Comparator<GreedyItem>() {
            public int compare(GreedyItem left, GreedyItem right) {
                double leftUnitPrice = left.totalValue / left.totalWeight;
                double rightUnitPrice = right.totalValue / right.totalWeight;
                if (leftUnitPrice > rightUnitPrice) {
                    return -1;
                } else if (leftUnitPrice == rightUnitPrice) {
                    return 0;
                } else {
                    return 1;
                }
            }
        });

        //从高到低依次取出豆子
        int leftPackCapacity = packCapacity;
        for (int i = 0; i < items.length; ++i) {
            if (leftPackCapacity > items[i].totalWeight) {
                leftPackCapacity -= items[i].totalWeight;
                beans.add(new GreedyItem(items[i]));
            } else {
                double unitPrice = items[i].totalValue / items[i].totalWeight;
                double packWeight = leftPackCapacity;
                double packValue = packWeight * unitPrice;
                beans.add(new GreedyItem(items[i].name, packWeight, packValue));
                leftPackCapacity = 0;
                break;
            }
        }

        return beans;
    }

    public static void main(String[] args) {
        GreedyItem[] items = {
                new GreedyItem("黄豆", 100, 100),
                new GreedyItem("绿豆", 30, 90),
                new GreedyItem("红豆", 60, 120),
                new GreedyItem("黑豆", 20, 80),
                new GreedyItem("青豆", 50, 75)
        };

        LinkedList<GreedyItem> beans = packBean(100, items);

        double maxValue = 0;

        System.out.println("装了如下物品：");
        for (GreedyItem bean : beans) {
            maxValue += bean.totalValue;
            System.out.println(bean.name + " " + bean.totalWeight);
        }

        System.out.println("总价值：" + maxValue);
    }
}

class GreedyItem {
    String name;
    double totalWeight;
    double totalValue;

    GreedyItem(String name, double totalWeight, double totalValue) {
        this.name = name;
        this.totalWeight = totalWeight;
        this.totalValue = totalValue;
    }

    GreedyItem(GreedyItem item) {
        this.name = item.name;
        this.totalWeight = item.totalWeight;
        this.totalValue = item.totalValue;
    }
}