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2-dimensional array help


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#1 SaintForHire   Members   -  Reputation: 115

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Posted 23 July 2013 - 09:28 PM

I've tried many different variations of the following code. I've even tried using the void function as the hub for the increase function, but I can't seem to figure it out. I feel like I'm really close, but I just don't get it.


#include <iostream>

#include <iomanip>

using namespace std;

 

const int division = 6;

const int quarters = 4;

 

void list(double [][quarters]);

double quarterlyIncrease(double [][quarters]);

 

int main()

{

    double arr[division][quarters];

 

    //This is where arr is given values.

    for (int i = 0; i < division; ++i)

    {

        cout << "Please enter the sales figures in division " << i + 1 << " for all four quarters\n";

        for (int j = 0; j < quarters; ++j)

        {

            cout << "Quarter " << j + 1 << ": $";

            cin >> arr[i][j];

            if (arr[i][j] < 0)

            {

                cout << "Please enter a positive sales figure: $";

                cin >> arr[i][j];

            }

        }

        cout << endl;

    }

 

    double increases = quarterlyIncrease(arr);

    list(arr);

}

 

//This is where the list of all the division's sales during each quarter are outputted.

void list(double arr[][quarters])

{

    for (int i = 0; i < division; ++i)

    {

        double total;

        double increase = 0.0;

        cout << "Division " << i + 1 << " Sales\n";

        cout << "------------------------\n";

        cout << setprecision(2) << fixed;

        for (int j = 0; j < quarters; ++j)

        {

            cout << "The sales for Quarter " << j + 1 << ": $" << arr[i][j] << endl;

            double increases = quarterlyIncrease(arr);

            if (j > 0)

            {

                cout << "The increase from the previous quarter: $" << increases;

                cout << endl;

            }

        }

        cout << endl;

    }

}

 

double quarterlyIncrease(double arr[][quarters])

{

    double total = 0.0;

    double increase = 0.0;

    for (int i = 0; i < division; ++i)

    {

        for(int j = 0; j < quarters; ++j)

        {

            increase += arr[i][j];

            if (j > 0)

            {

                total = arr[i][j];

                increase += total - increase;
                return increase;
            }
        }
    }
}

I don't know how to make the increase between each quarter work.

Basically, when I try to output the increase (no matter how I've tried it) it seems to output either the first number entered into the 2 dimensional array, or the second number entered in as the 2 dimensional array. 

 

The current code shows it as the second number entered (meaning quarter 2 in division 1 is always the increase throughout the entire code).

 

Thanks for the help!

 

 



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#2 Pink Horror   Members   -  Reputation: 1055

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Posted 23 July 2013 - 10:43 PM


                increase += total - increase;
                return increase;

 

You are return as soon as you find some j > 0, which is quarter 2 in division 1.

 

(ignoring any floating point strangeness)

 

increase += total - increase;

 

is the same as:

 

increase = increase + total - increase;

 

is the same as

 

increase = total;

 

So, quarterlyIncrease just does this:

 

return arr[0][1];

 

I cannot figure out what you want this code to do, but I hope I can help you see what it does do.

 

I've looked at it a little more. From the list function, I see you want to call quarterlyIncrease for each iteration. That's ok. You only provide the array as input, which means that it naturally would return the same thing over and over, unless you has some sneaky globals in there. You should pass your quarter and division indices into this function.


Edited by Pink Horror, 23 July 2013 - 10:48 PM.


#3 Yrjö P.   Crossbones+   -  Reputation: 1412

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Posted 24 July 2013 - 04:25 AM

I'm not sure why you even call quarterlyIncrease here:

double increases = quarterlyIncrease(arr);
if (j > 0)
{
    cout << "The increase from the previous quarter: $" << increases;
    cout << endl;
}

// when it seems like you actually want this?

if (j > 0) {
    cout << "The increase from the previous quarter: $" << arr[i][j] - arr[i][j-1];
    cout << endl;
}

As an aside, using raw arrays is not generally considered good style. It makes your life harder. Prefer vector<vector<double>>, or possibly vector<array<double, 4>> if you have C++11 standard library.



#4 Paradigm Shifter   Crossbones+   -  Reputation: 5094

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Posted 24 July 2013 - 08:55 AM

What they probably need is to track the last quarter value when it is output. The above solution doesn't work for the first quarter of a year (need to compare to last quarter of previous year).

 

Pseudo code:

 

isFirstValue = true

previousValue = 0

 

while moreDataToOutput():

  currentValue = getQuarterlyValue()

  output "sales for this quarter = $" currentValue

  if not isFirstValue output "quarterly increase = $" currentValue - previousValue

  isFirstValue = false

  previousValue = currentValue

end while


Edited by Paradigm Shifter, 24 July 2013 - 08:56 AM.

"Most people think, great God will come from the sky, take away everything, and make everybody feel high" - Bob Marley

#5 SaintForHire   Members   -  Reputation: 115

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Posted 24 July 2013 - 07:57 PM

Thx all for the help. It helped immensely.

 

 

I'm not sure why you even call quarterlyIncrease here:

double increases = quarterlyIncrease(arr);
if (j > 0)
{
    cout << "The increase from the previous quarter: $" << increases;
    cout << endl;
}

// when it seems like you actually want this?

if (j > 0) {
    cout << "The increase from the previous quarter: $" << arr[i][j] - arr[i][j-1];
    cout << endl;
}

As an aside, using raw arrays is not generally considered good style. It makes your life harder. Prefer vector<vector<double>>, or possibly vector<array<double, 4>> if you have C++11 standard library.

 

This made the most sense to me and makes my code A LOT smaller, so I used this as my personal choice fix.

 

Also thank you Pink. I think my code was confusing me a little bit, so I just started throwing random stuff at it to get it to work, which just confused me more.






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