背包问题

package dp_bag;

/**
 * 有编号分别为a,b,c,d,e的五件物品，它们的重量分别是2,2,6,5,4，
 * 它们的价值分别是6,3,5,4,6，现在给你个承重为10的背包，
 * 如何让背包里装入的物品具有最大的价值总和？
 * 
 * 01背包的状态转换方程 f[i,j] = Max{ f[i-1,j-Wi]+Pi( j >= Wi ),  f[i-1,j] }
 * @author Administrator
 *
 */

public class Bag {

	private static char [] bags  = {'e','d','c','b','a'};
	private static int [] checked_bags  = new int[5];
	private static int [] volume = {4,5,6,2,2};
	private static int [] price  = {6,4,5,3,6};
	private static int capacity  = 10;
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int k = f(4, capacity);
		System.out.println(k);
		
		print_bags();
		
//		print_value();
	}

	public static int f(int i, int j) {
		if(i<0)
			return 0;
		if(j<=0)
			return 0;
		//不装入
		int a = f(i-1,j);
		//装入
		int b;
		if(j-volume[i]>=0)//装得下
			b = f(i-1,j-volume[i]) + price[i];
		else//装不下
			b = 0;
		//记录选择了哪些背包
		if(a>b)
			checked_bags[i] = 0;
		else
			checked_bags[i] = 1;
		
		return a>b?a:b;
	}
	
	public static void print_value(){
		for(int i=0; i<5; i++){
			for(int j=1; j<11; j++){
				System.out.print(f(i,j) + "  ");
			}
			System.out.println();
		}
	}
	
	public static void print_bags(){
		for(int i=0; i<5; i++){			
			if(checked_bags[i]==1){
				System.out.print(bags[i]+" ");
			}
		}
	}
}

很简洁的代码，教程可参考点击打开链接