背包问题（Kanpsack Problem）

问题说明：

假设一个背包的负重最大可达8公斤，而希望在背包内放置负重范围你价值最高的物品。

class Fruit {
    private String name;
    private int size;
    private int price;
    
    public Fruit(String name, int size, int price) {
        this.name = name;
        this.size = size;
        this.price = price;
    }
    
    public String getName() {
        return name;
    }

    public int getPrice() {
        return price;
    }

    public int getSize() {
        return size;
    }
}

public class Knapsack {
    public static void main(String[] args) {
        final int MAX = 8;
        final int MIN = 1;
        int[] item = new int[MAX+1]; 
        int[] value = new int[MAX+1];  

        Fruit fruits[] = {
                new Fruit("李子", 4, 4500), 
                new Fruit("苹果", 5, 5700), 
                new Fruit("桔子", 2, 2250), 
                new Fruit("草莓", 1, 1100), 
                new Fruit("甜瓜", 6, 6700)}; 

        for(int i = 0; i < fruits.length; i++) { 
            for(int s = fruits[i].getSize(); s <= MAX; s++) { 
                int p = s - fruits[i].getSize(); 
                int newvalue = value[p] + 
                                   fruits[i].getPrice(); 
                if(newvalue > value[s]) {// 找到阶段最佳解 
                    value[s] = newvalue; 
                    item[s] = i; 
                } 
            } 
        } 

        System.out.println("物品\t价格"); 
        for(int i = MAX; 
            i >= MIN; 
            i = i - fruits[item[i]].getSize()) { 
            System.out.println(fruits[item[i]].getName()+ 
                    "\t" + fruits[item[i]].getPrice()); 
        } 

        System.out.println("合计\t" + value[MAX]);  
    }
}