How to make my arrays use Dynamic Memory Allocation?

[dusky trail]

Program takes in 5 teams no matter what right now but I want the user to state how many teams there are first, then go off of that number instead of the default 5.

I like jumping out of airplanes*/
#include <iostream>
using namespace std;

void initializeArrays(string names[], int wins[], int size);
void sortData(string names[], int wins[], int size);
void displayData(string names[], int wins[], int size);

int main()
{
    const int NUM_TYPES = 5;
    int numTeams;
    int* ptr = NULL;

    cout << "How many teams will you enter?: ";
    cin >> numTeams;

    
    string names[NUM_TYPES] = {};
    int wins[NUM_TYPES] = {};
    initializeArrays(names, wins, 5);
    sortData(names, wins, 5);
    displayData(names, wins, 5);


    return 0;
}

void initializeArrays(string names[], int wins[], int size) {
    int rotations[5] = { 1, 2, 3, 4, 5 };
    for (int i = 0; i < 5; i++) {
        cout << "Enter team #" << rotations[i] << ": ";
        cin >> names[i];
        cout << "Enter the wins for team #" << rotations[i] << ": ";
        cin >> wins[i];

    } return;

}
void sortData(string names[], int wins[], int size) {

    for (int j = 0; j < 5; j++) {

        for (int i = 0; i < 5 - 1; i++) {
            if (wins[i] < wins[i + 1]) {
                string temp;
                temp = names[i];
                names[i] = names[i + 1];
                names[i + 1] = temp;
                int x = wins[i];
                wins[i] = wins[i + 1];
                wins[i + 1] = x;

            }
        }
    }
    return;
}
void displayData(string names[], int wins[], int size) {
    int rotations[5] = { 1, 2, 3, 4, 5 };
    cout << "League Standings:" << endl;
    for (int i = 0; i < 5; i++) {
        cout << names[i] << ": " << wins[i] << endl;
    }

    return;
}

[rapid jungle]

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[quiet dome]

is there a reason you have to use C-style arrays instead of std::vector?

if so then you need to use new (or malloc) if you want an array whose size is not known until runtime

[dusky trail]

Yeah trying to learn how the pointers work without the vectors

[normal trail]

int *arr = new int[size] where size can be any integer

[dusky trail]

Apply this to the names and wins arrays?

tried that but the name wouldn't work, and with the name the int wouldnt work, etc

[normal trail]

i didnt read your code im just telling you how to use dynamic memory allocation in the arrays

[dusky trail]

Ah, well I know what it looks like but I'm not sure what to change here as what I thought I needed to do didn't work

I did that, wasn't running 😦

[normal trail]

whats int rotations[5] for ??

[dusky trail]

Just to make it the same as the default size of the names and prices array

So there's something else I need to work on lol

[normal trail]

i didnt understand your question

you make 5 arrays and then input one team in each array right ?

[dusky trail]

nono there is only two arrays

price and wins

in main

[normal trail]

names and wins ?

[dusky trail]

    int wins[NUM_TYPES] = {};```

[normal trail]

so you want to enter as many names as the user wants in the names array right ?

and as many wins as the user wants in the wins array

[dusky trail]

ye

[normal trail]

okay

[dusky trail]

If theres 4 games, it asks the user 4 times for team names and the wins

[normal trail]

this firstly to make variable length arrays is bad practice

[dusky trail]

Gotchya

[normal trail]

int num_of_elements = 0;
cin >> num_of_elements; //user enters the number of elements in the array
int *arr = new int[num_of_elements]; // allocates memory for the number of elements given 
for (int i = 0; i < num_of_elements; i++)
  cin >> arr[i]; // taking input in the array

if you use int arr[n] the n can be more than what more than what memory you have on the stack and your program may crash

[dusky trail]

which is the way I originally did it right?

[normal trail]

so int *array_name = new int[size] allocates memory on the heap and gives you a pointer to the first element of the array (the name of the array always points to the first element of the array)

[normal trail]

ye

[dusky trail]

So I would replace the string names[NUM_TYPES] with that array

[normal trail]

for a string array

int num_of_elements = 0;
cin >> num_of_elements; //user enters the number of elements in the array
string *arr = new string [num_of_elements]; // allocates memory for the number of elements given 
for (int i = 0; i < num_of_elements; i++)
  cin >> arr[i]; 

just change the type

[dusky trail]

One sec, ima try this then

Two things: so I need two pointers then?

And, I did that still doesn't work:

int *wins = new int[NUM_TYPES] = {};```

[normal trail]

thats wrong

the new keyword just allocates memory for you to use

https://www.geeksforgeeks.org/what-is-dynamic-memory-allocation/

[dusky trail]

int* wins = new int[numTeams];```

Gotchya okay so, now I know how to write an array with a pointer

Gotta do the same for the string array right?

[normal trail]

yeah

also after using the array at the end of the program you should free the allocated memory

[dusky trail]

Well, before that it still goes over 5 times by default 😦

[normal trail]

using

delete []array_name; 

[dusky trail]

yeah so im still confused on how its dynamic if my functions still use (int j = 0; j < 5; j++)

[normal trail]

your function should use j < size

[dusky trail]

ahhh one sec

okay so it still goes to 5, but breaks if I say anything less than 5 teams

[normal trail]

Dynamic memory allocation with new
Memory allocated dynamically is taken from the heap memory. Every program at runtime is allocated a temporary memory called stack memory.
int arr[n];
the above code is trying to create a array of user input length but this is bad practice and in most cases not allowed by the compiler as the memory is being used from the stack and the input may be greater than the memory available in the stack thus causing the program to crash.
To avoid this memory is allocated dynamically using the new keyword. This memory is allocated in the heap. the memory cannot be allocated to a variable in as the address is being allocated and hence a pointer is used to store the address.

[dusky trail]

So I can logically understand that, but I can't visually see that in code

[normal trail]

no lol

[dusky trail]

mb 😦

[rapid jungle]

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