闲来无事敲的几行代码,贪心算法的核心在于先排序,找到一种规律,然后根据问题要求遍历列表解决问题.

贴出代码:

package 背包问题贪心算法;


import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;


public class Main {


	public static void main(String[] args) {
		Scanner input=new Scanner(System.in);
		int testnum=input.nextInt();
		for (int i = 0; i < testnum; i++)
		{
			int goodsNum=input.nextInt();
			int bagContain=input.nextInt();
			ArrayList<Goods> goodsList=new ArrayList<Goods>();
			for(int j=0;j<goodsNum;j++)
			{
				Goods goods=new Goods();
				goods.value=input.nextInt();
				goods.weight=input.nextInt();
				goodsList.add(goods);
			}
			Collections.sort(goodsList);
			int bagValue=0;
			for(int k=0;k<goodsList.size();k++)
			{
				if (bagContain!=0) {
					if (bagContain-goodsList.get(k).weight>0) {
						bagContain-=goodsList.get(k).weight;
						bagValue+=goodsList.get(k).value*goodsList.get(k).weight;
					}		
					else if (bagContain-goodsList.get(k).weight<=0) {
						bagValue+=goodsList.get(k).value*bagContain;
						bagContain=0;
					}
				}
			}
			System.out.println(bagValue);
		}
		input.close();
	}
	
	public static class Goods implements Comparable<Goods>
	{
		public int value;
		public int weight;
		@Override
		public int compareTo(Goods o) {
			
			if (this.value>o.value) {
				return -1;
			}
			else if (this.value==o.value) {
				return 0;
			} 
			else {
				return 1;
			}
		}
		
	}
}