Java描述贪心算法解决背包问题

来源：互联网发布：道路设计常用数据手册编辑：程序博客网时间：2024/05/16 08:21

思路: 首先将物品根据性价比排好序在一个集合里,性价比=价格/重量...

然后根据性价比从大到小依次依次放入背包,如果没办法放入这个物品的全部,就放入一部分,如果可以放入全量物品,就放入全量物品。

Main.java的代码

import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;/** * Created by HuLuo on 2016/2/16. */public class Main{    //背包总质量    private static double M = 20;    //物品数量    private static int number = 3;    public static void main(String[] args)    {        MyObject myObject1 = new MyObject( 18, 25 );        MyObject myObject2 = new MyObject( 15, 24 );        MyObject myObject3 = new MyObject( 10, 15 );        ArrayList<MyObject> myObjects = new ArrayList<MyObject>( number );        myObject1.priceRatio = ( myObject1.price * 1.0 ) / ( myObject1.weight );        myObject2.priceRatio = ( myObject2.price * 1.0 ) / ( myObject2.weight );        myObject3.priceRatio = ( myObject3.price * 1.0 ) / ( myObject3.weight );        myObjects.add( myObject1 );        myObjects.add( myObject2 );        myObjects.add( myObject3 );        //根据物品的性价比将集合中的物品做一个排序 ,按照性价比从大到小排列        Collections.sort( myObjects, new Comparator<MyObject>()        {            @Override            public int compare(MyObject o1, MyObject o2)            {                if(o1.priceRatio > o2.priceRatio)                {                    return -1;                }                else                    return 1;            }        } );        MyObject temp = null;        for(int i = 0; i < number && M > 0; i++)        {            temp = myObjects.get( i );            if(M >= temp.weight)            {                M = M - temp.weight;                temp.x = 1.0;            }            else            {                temp.x = ( M * 1.0 ) / temp.weight;                M = M - ( temp.weight * temp.x );            }        }        for(MyObject myObject : myObjects)        {            System.out.println( "物品价格是:" + myObject.price + "的物品, 装入比例是:" + myObject.x );        }    }}

MyObject.java文件的代码

/** * Created by HuLuo on 2016/2/16. *//** * 物品对象 */public class MyObject{    public int weight = 0;    public int price = 0;    //装入的比例    public double x = 0;    //性价比    public double priceRatio = 0 ;    public MyObject(int weight, int price)    {        this.weight = weight;        this.price = price;    }}

1 0