分支定界背包 Java

Posted 2023-02-16

【中文标题】分支定界背包 Java

【英文标题】：Branch and Bound Knapsack Java

【发布时间】：2015-11-22 19:41:03

【问题描述】：

import java.io.*;
import java.util.*;

class node
    int level;
    int profit;
    int weight;
    int bound;


public class KnapsackBB
        public static void main(String args[])throws Exception
                int maxProfit;
                int N;
                int W;
                int wt;
                int vl;
                int maxVal;

                Scanner input = new Scanner(System.in);

                System.out.println("Please enter the number of items: ");
                N = input.nextInt();
                System.out.println("Please enter the capacity of the Knapsack: ");
                W = input.nextInt();

                int[] Vl = new int[N];
                int[] Wt = new int[N];

                for(int i = 0; i < N; i++)
                        System.out.println("Please enter the weight anc value of item " + i + ": ");
                        wt = input.nextInt();
                        vl = input.nextInt();

                        Wt[i] = wt;
                        Vl[i] = vl;
                


                //for(int i  = 0; i < 1000; i++)
                        maxVal = knapsack(N, Vl, Wt, W);
                //

                System.out.println(maxVal);

        


        public static int bound(node u, int n, int W, int[] pVa, int[] wVa)
                int j = 0, k = 0;
                int totweight = 0;
                int result = 0;

                if (u.weight >= W)
                        return 0;
                
                else
                        result = u.profit;
                        j = u.level + 1;
                        totweight = u.weight;

                        while ((j < n) && (totweight + wVa[j] <= W))
                                totweight = totweight + wVa[j];
                                result = result + pVa[j];
                                j++;
                        

                        k = j;

                        if (k < n)
                                result = result + (W - totweight) * pVa[k]/wVa[k];
                        
                        return result;
                
        

        public static int knapsack(int n, int[] p, int[] w, int W)
                Queue<node> Q = new LinkedList<node>();
                node u = new node();
                node v = new node();
                int[] pV = new int[p.length];
                int[] wV = new int[w.length];
                Q.poll();

                for (int i = 0; i < n; i++)
                        pV[i] = p[i];
                        wV[i] = w[i];
                

                v.level = -1;
                v.profit = 0;
                v.weight = 0;

                int maxProfit = 0;

                //v.bound = bound(v, n, W, pV, wV);
                Q.add(v);

                while (Q.size() > 0)
                        v = Q.remove();

                        if (v.level == -1)
                                u.level = 0;
                        
                        else if (v.level != (n - 1))
                                u.level = v.level + 1;
                        

                        u.weight = v.weight + w[u.level];
                        u.profit = v.profit + p[u.level];

                        u.bound = bound(u, n, W, pV, wV);

                        if (u.weight <= W && u.profit > maxProfit)
                                maxProfit = u.profit;
                        

                        if (u.bound > maxProfit)
                                Q.add(u);
                        

                        u.weight = v.weight;
                        u.profit = v.profit;

                        u.bound = bound(u, n, W, pV, wV);

                        if (u.bound > maxProfit)
                                Q.add(u);
                        

                
                return maxProfit;
        

我的程序有问题，因为我得到了错误的输出。我已经从我在网上找到的另一个程序从 C++ 转换并且它可以正常工作。

输入：

4

6

2 10

3 12

4 5

3 15

输出应该是：

22

得到的输出：

12

【参考方案1】：

您的复制技巧还有很多不足之处 - 如果您添加了指向原始来源的链接，那将会很有帮助。

好像你已经添加了行

u.weight = v.weight;
u.profit = v.profit;
u.bound = bound(u, n, W, pV, wV);
if (u.bound > maxProfit)
    Q.add(u);

两次。至少这提供了您正在寻找的“22”答案。

也就是说，该解决方案远非面向对象和一般的 Java 风格。