Empty places at the end of the arrays C ++

Question

1.00/5 (1 vote)

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C#

void HousingRegister::printBythePrice(string *array, float max)const {
            int index = 0;
            for (int i = 0; i <nrOfHouses; i++)
            {
                if (housing[i]->getRent() <= max)
                {
                    array[index] = housing[i]->toString();
                    index++;
                }
            }
        }

        //mainfunc

        void printBythePrice(const HousingRegister &house){

            float max;
            string *arr = new string[house.getnrOfHouses()];
            cout << "Enter the price: ";
            cin >> max;
            house.printBythePrice(arr, max);
            for (int i = 0; i < house.getnrOfHouses(); i++)
            {
                cout << arr[i];
            }
            delete[] arr;
        }

What I have tried:

It is the wrong size of the array. You need to implement functionality so you do not have empty places at the end of the array.

Posted 30-May-16 13:38pm

Member 12549902

Updated 30-May-16 14:18pm

PIEBALDconsult

v2

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Comments

Member 12549902 30-May-16 20:09pm

it is the wrong size of the array. You need to implement functionality so you do not have empty places at the end of the array. This is my question? Can you fix this mistake? cheek this code careful. i need an answer buy tonight

Philippe Mori 30-May-16 21:04pm

As explained in solution 1, code design is wrong. I would suggest you to use std::vector and STL algorithm to solve that problem.

If this problem is academic and you haven't yet seen STL, then you should add a parameter for the size.

By the way, I would recommand you to use array syntax instead of pointer syntax to make it clearer that you are passing an array.

Member 12549902 31-May-16 3:36am

Plz give me an exemple code how you wuold inplement it?

Philippe Mori 31-May-16 9:04am

All necessary information is provided. If you don't understand, then read your course note again. If you don't make any effort, you won't learn anything.

In that case, you have to know how many items satisfy the condition so you have to return the value somehow.

Member 12549902 31-May-16 9:22am

void printBythePrice(const HousingRegister &house){

float max;
int index = 0;
string *arr = new string[house.getnrOfHouses()];
cout << "Enter the price: ";
cin >> max;

house.printBythePrice1(arr, &index, max);

house.getnrOfHouses()==index;

for (int i = 0; i < house.getnrOfHouses(); i++)
{
cout << arr[i];
}
delete[] arr;
}

void printStrings(string stringArray[], int nrOfStrings)
{
for (int i = 0; i < nrOfStrings; i++)
{
cout << endl << stringArray[i] << endl;
}
}

void HousingRegister::printBythePrice(string *array, int *index, float max)const {

for (int i = 0; i <nrofhouses; i++)="" {
="" if="" (housing[i]="">getRent() <= max)
{
array[*index] = housing[i]->toString();
index++;
}
}
}
Like this you mean? I am really tring evrything to learn doing my best, studing 8 h a day 5 days a week, some learn fast same learn slow. I am not lazzy person. I want to learn, this function works good, but i know there is a better way of fixing this. I trying i am doing my best, thats why i am asking for help. I am sorry if i look like a lazzy person, but i am just a bigginer in c++.

Philippe Mori 31-May-16 9:55am

This is probably a good solution given what you learn... except for the line house.getnrOfHouses()==index; (and the following loop condition).

Member 12549902 31-May-16 10:04am

Index hast to point to some adress? i Just need to delete this line
house.getnrOfHouses()==index;

Sorry my english i not my first lenguage. Hope you understand me.

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Sergey Alexandrovich Kryukov · Accepted Answer · 2016-05-30T14:18:00

Solution 1

The problem is: the whole idea of such code design is wrong. This way, not only you can get "empty places", but, generally, just some garbage, uninitialized memory. Worse, you can face addressing of memory beyond the memory allocated for the array, with the exception based on General Protection Fault, or, worse, writing garbage beyond that memory area, with unpredictable results.

At the same time, such problems are resolved in really simple ways. First, note that your function does not receive any information on the allocated or assumed length of the array; you receive just a pointer to the beginning of the arrays memory, if it is correct.

Now, you have to think where the knowledge on required array size come from. Let's say, it is known to the caller. Fine, the caller should allocated the array and pass the actual array length to the function.

More difficult (and less desirable) cases when the length becomes known inside the function, as a result of its internal calculations. In this case, you have to allocate the array inside the function and return it.

That's all; as simple as that.

—SA

Posted 30-May-16 14:18pm

Sergey Alexandrovich Kryukov

Comments

Member 12549902 30-May-16 20:29pm

Thank you, can you give me an exempel you can you inplement it?
Plz i have tried how to fix it for more than 3 weeks and i didnt succed.

Sergey Alexandrovich Kryukov 30-May-16 20:32pm

I don't understand what else you may need. The issue is simple as hell.
And you did not tell me which of the two cases you have.
—SA

Member 12549902 31-May-16 2:47am

Both are conected. Need to print all houses that has the rent price less than the abount i wrote.
Would you inplement such a code.. without empty plases, and not getin garbage, uninitialized memory?
I am sorry for this stupit question but i am new att programing and i dont understand all.

Sergey Alexandrovich Kryukov 31-May-16 9:13am

Sorry, no. You know the array length either outside of the function (in the caller) or determine it inside. Two cases. What is it?
—SA

Member 12549902 31-May-16 9:28am

you mean array[index]?

Sergey Alexandrovich Kryukov 31-May-16 9:32am

No, array[index] is not an array. I mean the function parameter "array". (What else?)
—SA

Member 12549902 31-May-16 9:35am

As parameters i have (string *array, float max)
So you mean i should have the index as parameter too?

void printByprice(string* array, int *index ,float max)

Member 12549902 31-May-16 9:40am

The length is nrOfelements as i have, writen: nrOfHouses.

and house.getnrOfHouses() int the other func

Yeah i know you are not the frist saying i am the worse. I hear that often.

Sergey Alexandrovich Kryukov 31-May-16 9:42am

Please stop it. No one here really told you that about you.
—SA

Member 12549902 31-May-16 9:46am

I don't mean here, here is everyone nice, thank you for your patience and good exponation, it's me that i am dumb.

Sergey Alexandrovich Kryukov 31-May-16 10:00am

Okay, I'll tell your, but please don't take it as offense.
You should better stop playing this "dump" card. This is called "whining". If you feel frustrating, it's better not to show to other people; you have to learn to control yourself. Instead, just focus on learning and work. On each step, set yourself a realistic goal. If you are not strong enough for the goal, step back, to a more elementary thing and solve the problem. Don't give up. Be independent.
—SA

Member 12549902 31-May-16 10:28am

Så true.. well said. Thank you så much

Sergey Alexandrovich Kryukov 31-May-16 10:31am

:-)

Sergey Alexandrovich Kryukov 31-May-16 9:41am

I'm coming to conclusion that you have to learn the language and basics of general programming from scratch.

I said, if you pass an array this way, you also have to pass its length:
printBythePrice(string *array, int arrayLength, float max) const.

Length, not index.

—SA

Member 12549902 31-May-16 9:50am

void HousingRegister::printBythePrice(string *array, int arrayLength, float max)const {

int index = 0;
for (int i = 0; i <nrofhouses; i++)
="" {
="" if="" (housing[i]-="">getRent() <= max)
{
array[index] = housing[i]->toString();
index++;
arrayLenght=index;
}
}
}

Sergey Alexandrovich Kryukov 31-May-16 9:54am

No. arrayLength is input parameter, it's useless to assign any value to it.
—SA

Member 12549902 31-May-16 9:59am

for(int i; i

Member 12549902 31-May-16 10:09am

Can you please cheek my code that i wrote, before?
Mabey thats is the sulution? on the top of the page.

Sergey Alexandrovich Kryukov 31-May-16 10:22am

for (int index = 0; index < arrayLength; ++index)
{
// ...
array[index] = //...
}

Member 12549902 31-May-16 10:42am

void HousingRegister::printBythePrice(string *array, int araylenght, float max)const {

int index = 0;
for (index = 0; index <araylenght; i++)
="" {
="" if="" (housing[i]-="">getRent() <= max)
{
array[index] = housing[i]->toString();
index++;
}
}
}