How to fill a multidimensional array dependant on variables

Question

The program I am working on is a simple shipping program. What I am having difficulty with is populating a multidimensional array factoring in certain variables.

Example

320 items need to be shipped out to 1 receiver using different box sizes.

XL can hold 50 items
LG can hold 20 items
MD can hold 5 items
SM can hold 1 items

Use the least number of boxes so far.

Code

This is my code so far.

import java.util.Scanner;

public class Shipping {
    public static void main(String [] args) {
        Scanner kbd = new Scanner(System.in);

        final int EXTRA_LARGE = 50;
        final int LARGE = 20;
        final int MEDIUM = 5;
        final int SMALL = 1;

        String sBusinessName = "";
        int iNumberOfGPS = 0;

        int iShipmentCount = 0;

        displayHeading(kbd);
        iShipmentCount = enterShipments(kbd);
        int[][] ai_NumberOfShipments = new int [iShipmentCount][4];
        String[] as_BusinessNames = new String [iShipmentCount];

        for (int iStepper = 0; iStepper < iShipmentCount; iStepper++) {
            sBusinessName = varifyBusinessName(kbd);
            as_BusinessNames[iStepper] = sBusinessName;
            iNumberOfGPS = varifyGPS(kbd);
            calculateBoxes(ai_NumberOfShipments[iStepper],iNumberOfGPS, EXTRA_LARGE, LARGE, MEDIUM, SMALL);
        }
        //showArray(as_BusinessNames);
    }

    public static void displayHeading(Scanner kbd) {
        System.out.println("Red River Electronics");
        System.out.println("Shipping System");
        System.out.println("---------------");

        return;
    }

    public static int enterShipments(Scanner kbd) {
        int iShipmentCount = 0;
        boolean bError = false;
        do {
            bError = false;
            System.out.print("How many shipments to enter? ");
            iShipmentCount = Integer.parseInt(kbd.nextLine());

            if (iShipmentCount < 1) {
                System.out.println("\n**Error** - Invalid number of shipments\n");
                bError = true;
            }
        } while (bError == true);

        return iShipmentCount;
    }

    public static String varifyBusinessName(Scanner kbd) {
        String sBusinessName = "", sValidName = "";
        do {
            System.out.print("Business Name: ");
            sBusinessName = kbd.nextLine();

            if (sBusinessName.length() == 0) {
                System.out.println("");
                System.out.println("**Error** - Name is required\n");
            } else if (sBusinessName.length() >= 1) {
                sValidName = sBusinessName;
            }
        } while (sValidName == "");

        return sValidName;
    }

    public static int varifyGPS(Scanner kbd) {
        int iCheckGPS = 0;
        int iValidGPS = 0;
        do {
            System.out.print("Enter the number of GPS receivers to ship: ");
            iCheckGPS = Integer.parseInt(kbd.nextLine());

            if (iCheckGPS < 1) {
                System.out.println("\n**Error** - Invalid number of shipments\n");
            } else if (iCheckGPS >= 1) {
                iValidGPS = iCheckGPS;
            }
        } while(iCheckGPS < 1);

        return iValidGPS;   
    }
    
    public static void calculateBoxes(int[] ai_ToFill, int iNumberOfGPS) {
        for (int iStepper = 0; iStepper < ai_ToFill.length; iStepper++)
    }

    //public static void showArray( String[] ai_ToShow) {
    //    for (int iStepper = 0; iStepper < ai_ToShow.length; iStepper++) {
    //        System.out.println("Integer at position " + iStepper + " is " + ai_ToShow[iStepper]);
    //    }
    //}
}

What is the problem exactly? It looks like you haven't figured out how to write calculateBoxes, but you seem to have started OK. However, I can't tell what this method needs to accomplish. It might help to have an array of four constants, instead of four separate constants EXTRA_LARGE, LARGE, etc. — ajb
– ajb, Commented Nov 11, 2014 at 23:53
Looks like this is a 0-1 Knapsack problem. Equation: 320 = 50a+20b+5c+1d Is there a box limit; weight? — Mr. Polywhirl
– Mr. Polywhirl, Commented Nov 11, 2014 at 23:54
The code is not yet complete as I am not sure how to write it out. What I want to do is take 320 items and place them into 6 XL boxes(320 - 300 = 20) and 1 LG box(20 - 20 = 0). I need to add this information in an array. What I was hoping to do was use the method calculateBoxes to do that. I am just not sure on how to structure the logic for it — Colin
– Colin, Commented Nov 12, 2014 at 0:33

Jason · Accepted Answer · 2014-11-12 05:12:37Z

1

Change your definition of calculateBoxes() to also take an array that represents the volume of each of the boxes (in your case this will be {50, 20, 5, 1}:

public static void calculateBoxes(int[] ai_ToFill, int[] boxVolumes, int iNumberOfGPS) {
    // for each box size
    for (int iStepper = 0; iStepper < ai_ToFill.length; iStepper++) {
        // while the remaining items to pack is greater than the current box size
        while(iNumberOfGPS >= boxVolumes[iStepper]) {
            // increment the current box type
            ai_ToFill[iStepper]++;
            // subtract the items that just got packed
            iNumberOfGPS -= boxVolumes[iStepper];
        }
    }
}

Another way of calculating this (using / and % instead of a while loop) would be:

public static void calculateBoxes(int[] ai_ToFill, int[] boxVolumes, int iNumberOfGPS) {
    // for each box size
    for (int iStepper = 0; iStepper < ai_ToFill.length; iStepper++) {
        if(iNumberOfGPS >= boxVolumes[iStepper]) {
            // calculate the number of boxes that could be filled by the items
            ai_ToFill[iStepper] = iNumberOfGPS/boxVolumes[iStepper];
            // reset the count of items to the remainder
            iNumberOfGPS = iNumberOfGPS%boxVolumes[iStepper];
        }
    }
}

edited Nov 12, 2014 at 5:12

answered Nov 12, 2014 at 1:13

Jason

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3 Comments

Colin Over a year ago

Thank you very much for this! I think the problem was that I was planning on importing each Box Size integer. Honestly, I was going to and use several IF, ELSE IF statements. I knew there had to be a better way.

ajb Over a year ago

@Colin If you want an even better way, use the / and % operators. You shouldn't have to write a loop that keeps subtracting 50 from a number, when you can use integer division to figure it out.

Jason Over a year ago

@ajb correct, however this might be simpler to understand in the first instance. I'll add that as an alternative.

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