第7周作业 -- 背包问题

1、背包问题。对上文中提到的背包问题提供的表1（第一行为背包总重量15，物品数量5；第2-6行，分别为第1-5件物品的重量与价值），W=15，编程计算最终背包所装物品的编号、总重量与总价值。

import java.io.File;  
import java.io.PrintWriter;  
import java.util.Scanner;  
  
public class Knapsack {  
    private int[] Value;//存储物品的价值  
    private int[] Weight;//存储物品的重量   
    private int allWeight;//背包容纳重量  
    private int allNum;//物品数量  
    private int BValue[][];//BValue[i][j]存储前i个物品的重量为j的最大价值  
    public Knapsack(int allWeight,int allNum){  
        this.setAllNum(allNum);  
        this.setAllWeight(allWeight);  
        this.Value=new int[allNum];  
        this.Weight=new int[allNum];  
        this.BValue=new int[allNum+1][allWeight+1];  
    }       
    public int[] getV() {  
        return Value;  
    }   
    public void setV(int[] v) {  
        this.Value = v;  
    }   
    public int[] getW() {  
        return Weight;  
    }    
    public void setW(int[] w) {  
        this.Weight = w;  
    }    
    public int[][] getBValue() {  
        return BValue;  
    }   
    public void setBValue(int[][] fValue) {  
        this.BValue = fValue;  
    }  
    public static void main(String[] args) {  
        String path="src/Knapsack.txt";  
        String resultPath="src/KnapsackResult.txt";  
        Scanner scanner=null;  
        PrintWriter pw=null;  
        try {  
            scanner=new Scanner(new File(path));  
            pw=new PrintWriter(new File(resultPath));  
            int allWeight=scanner.nextInt();//背包所能容纳的总重量  
            int allNum=scanner.nextInt();//物品数量  
            Knapsack kna= new Knapsack(allWeight,allNum);//初始化背包  
            int[] v=kna.getV();  
            int[] w=kna.getW();  
            int[][] BValue=kna.getBValue();  
            int i=1;  
            for(i=1;i<=allNum;i++){//初始化物品价值数组和重量数组  
                 w[i-1]=scanner.nextInt();  
                 v[i-1]=scanner.nextInt();  
            }  
            for(i=1;i<=allNum;i++){  
                BValue[i][0]=0;  
            }  
            for(i=1;i<=allWeight;i++){  
            	BValue[0][i]=0;  
            }  
            for(i=1;i<=allNum;i++){  
                for(int j=1;j<=allWeight;j++){  
                    if(j<w[i-1]){  
                    	BValue[i][j]=BValue[i-1][j];  
                    }else{  
                    	BValue[i][j]=Math.max(BValue[i-1][j], BValue[i-1][j-w[i-1]]+v[i-1]);  
                    }  
                }  
            }  
            System.out.println("背包中物品的最大价值是："+BValue[allNum][allWeight]);  
            kna.traceBack(v, w, BValue, allWeight, allNum);//求出物品编号和背包总重量  
            System.out.println("构造的二维表格输出结果：");  
            for(i=1;i<=allNum;i++){	//输出二维数组到文本文件KnapsackResult.txt中  
                for(int j=1;j<=allWeight;j++){  
                    System.out.print(BValue[i][j]+" ");  
                    pw.print(BValue[i][j]+" ");  
                }  
                System.out.println();  
                pw.println();  
            }  
        } catch (Exception e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }finally{  
            if(scanner!=null) scanner.close();  
            if(pw!=null)  pw.close();  
        }  
    }     
   
    public void traceBack(int[] v,int[] w,int[][] fvalue,int allWeight,int allNum){  
        int wupinNo[]=new int[allNum+1];  
        int j=allWeight;  
        for(int i=allNum;i>0;i--){  
            if(fvalue[i][j]>fvalue[i-1][j]){  
                wupinNo[i]=1;  
                j-=w[i-1];  
                if(j<0){  
                    break;  
                }  
            }  
        }  
        int sumWeight=0;//记录背包的总重量  
        System.out.println();  
        System.out.println("背包中物品的编号是：");  
        for(int i=1;i<=allNum;i++){  
            if(wupinNo[i]==1){  
                System.out.print(i+" ");  
                sumWeight+=w[i-1];  
            }  
        }  
        System.out.println();  
        System.out.println();  
        System.out.println("背包的总重量是："+sumWeight);  
        System.out.println();  
    }
	public void setAllWeight(int allWeight) {
		this.allWeight = allWeight;
	}
	public int getAllWeight() {
		return allWeight;
	}
	public void setAllNum(int allNum) {
		this.allNum = allNum;
	}
	public int getAllNum() {
		return allNum;
	}  
}