Storing a list of values

[chrisdudeperson]

Hi there,

I'm fairly new to C++ so apologies if this answer is fairly obvious

I have a list of integers that i wish to store in some kind of array. However i do not know how many integers are needed to be stored each time i run my program so i therefore cannot define a size for my array

What is the best way of dealing with something like this?

Thanks
Chris

[JLBorges]

Use a resizeable array. A std::vector<>
http://www.mochima.com/tutorials/vectors.html

[j3Rz8vqX]

Yeah, vectors are much nicer, but if you had to use a primitive dynamic array, the example below would be how to dynamically modify your array (it's size at least):

#include <iostream>
using namespace std;

//Function Prototypes:
void copyArray(int *&i_array,int *t_array,int i_size);
void changeArraySize(int *&i_array,int &i_size,int new_size);
void printArray(int *i_array,int i_size);

//The main function:
//No argument: Though you could easily do that...
int main()
{
    //Stub data: assuming 5 data were taken already.
//---------------------Declarations and Initializations-----------------------------||
    int i_size = 5;//our integer arrays size. Hard coded, but yours can be modified.

    int *i_array= new int[5];//Our hard coded integer array (pointer to it that is)

    int l_array[5] = {3,2,1,5,4};//Local array with values

//---------------------Actual Processing--------------------------------------------||
    copyArray(i_array,l_array,i_size);//copying array!

    printArray(i_array,i_size);//Printing before increment

    changeArraySize(i_array,i_size,i_size+1);//incrementing

    i_array[5] = 82;//Let us modify our new (supposedly empty slots) value:

    printArray(i_array,i_size);//Printing after increment

//---------------------Clean Up-----------------------------------------------------||
    delete []i_array;//We are done playing, let us free our memory at i_array.

    return 0;
}

//Simple copy service:
//Argument#1 is the array to be kept,
//argument#2 is the copy array to be copied,
//argument#3 is the number of elements copied.
void copyArray(int *&i_array,int *t_array,int i_size)//First argument by reference
{
    for(int i=0;i<i_size;i++)//Don't step out of bound(Less than max size)
    {
        i_array[i]=t_array[i];//Copy values : exactly like an array.
    }
}

//Simple increment service:
//Argument#1 is the pointer to array by reference,
//argument#2 is the number of old elements,
//argument#3 is the number of new elements.
void changeArraySize(int *&i_array,int &i_size,int new_size)//First argument by reference
{
    int *t_array = new int[new_size];//Create a new temporary array of new_size

    copyArray(t_array,i_array,i_size+new_size-i_size);
    //Math: Itself + the difference: (1,-1) or (0) if they're equal.

    delete []i_array;//Now we can release the old memory: Farewell...

    i_array = t_array;//Now we can copy/re-point: Re-assign pointer.

    t_array = 0;//Not necessary, but good practice : deallocate pointing device, not delete.

    i_size+=new_size-i_size;//Modify our logical size.
    //Math: Itself + the difference (1,-1) or (0) if they're equal.
}

//Simple printing service:
//Argument#1 is the array,
//argument#2 is the size of the array.
void printArray(int *i_array,int i_size)
{
    cout<<"===Printing==="<<endl;
    for(int i=0;i<i_size;i++)//Don't step out of bound(Less than max size)
    {
        cout<<"At index["<<i<<"]: "<<i_array[i]<<endl;
    }
    cout<<"===Printing==="<<endl<<endl;
}

I provided a lot of comments, hopefully it doesn't cause reading issues.

Good day.

Tip: Don't be intimidated, there aren't too many line of code per function; maybe 10 max.