to merge two arrays

[Pulock2009]

compiled on turbocpp 4.5.....error is that the final merged array is much bigger with garbage values...please help to find the mistake in this program...

//cpp program to concatenate 2 arrays
#include<iostream.h>
#include<conio.h>
//the class
class array
{
		private:
		int a[40];
		int n;
		public:
		void getdata();
		void concatenate(array &a1,array &a2);
		void showdata(array &a);
};
void array::getdata()
{
		cout<<"\n How many?";
		cin>>n;
		cout<<"\n Enter the elements:";
		for(int i=0;i<n;i++)
		{
			  cin>>a[i];
		}
}
void array::showdata(array &a)
{
		for(int i=0;i<a.n;i++)
		{
			  cout<<"\n"<<a.a[i];
		}
}
//concatenation or merge function for the two arrays
void array::concatenate(array &a1,array &a2)
{
		array a3;
		for(int i=0,k=0;i<a1.n;i++,k++)
		{
			  a3.a[k]=a1.a[i];
		}
		for(int j=0;j<a2.n;j++,k++)
		{
			  a3.a[k]=a2.a[j];
		}
}
void main()
{
		array a1,a2,a3;
		a1.getdata();
		a1.showdata(a1);
		a2.getdata();
		a2.showdata(a2);
		a3.concatenate(a1,a2);
		a3.showdata(a3);
		getch();
}

[Salem]

Your concatenate stores all the results in a local var a3, not the 'this' instance of a.

[Pulock2009]

Your concatenate stores all the results in a local var a3, not the 'this' instance of a.

void array::concatenate(array &a1,array &a2)
{
		for(int i=0,k=0;i<a1.n;i++,k++)
		{
			  this.a[k]=a1.a[i];
		}
		for(int j=0;j<a2.n;j++,k++)
		{
			  this.a[k]=a2.a[j];
		}
}

should not the above modification solve the problem? Haven't done OOP for a long time. sorry for the inconvenience.

[Salem]

> should not the above modification solve the problem?
It might, if you also update the other private member variable with the appropriate value.

[jocdrew21]

//cpp program to concatenate 2 arrays
#include<iostream>

using namespace std;

//the class
class my_array
{
private:
    int a[40];
    int n;
public:
    my_array();
    void getdata();
    void concatenate(my_array &a1,my_array &a2);
    void showdata(my_array &a);
};
void my_array::getdata()
{
    cout<<"\n How many?";
    cin>>n;
    cout<<"\n Enter the elements:";
    for(int i=0;i<n;i++)
    {
        cin>>a[i];
    }
}
my_array::my_array()
{
    for (int i=0; i<40; ++i)
    {
        a[i]=0;
    }
    n=0;
}
void my_array::showdata(my_array &a)
{
    for(int i=0;i<a.n;i++)
    {
        cout<<"\n"<<a.a[i];
    }
}
//concatenation or merge function for the two arrays
void my_array::concatenate(my_array &a1,my_array &a2)
{
    my_array a3;
    for(int i=0,k=0;i<a1.n;i++,k++)
    {
        a3.a[k]=a1.a[i];
    
    for(int j=0;j<a2.n;j++,k++)
    
        a3.a[k]=a2.a[j];
    }
}
int main()
{
    my_array a1,a2,a3;
    a1.getdata();
    a1.showdata(a1);
    a2.getdata();
    a2.showdata(a2);
    a3.concatenate(a1,a2);
    a3.showdata(a3);
    
    return 0;
}

Look into namespaces if you want to name something like "array" and not actually use one. Actually that is really a bad idea but it would be good practice so give it a try. Your main was void and it should be int, you didn't have a return value in your main as well.. Your loop ended and you still tried to implement a char with the above one. Watch your brackets and pay attention to your complier warnings. Also you had no constructor.

You really should be using an vector here. They are so much easier to work with and setting the size of your array while the program is running is very poor practice. The code I post is not prefect and needs work so if this is a homework assignment don't submit this. Look at the loop and think about a vector and easy it would be to merge to the using insert. Look up insert at cplusplus.com is your are unfamiliar with this.

Look at the code and I will do the best I can to help.

[jocdrew21]

I apologize for all the grammar errors in the above statement. Looks like I should proofread my posts if I am a little tipsy.

[jeedi khan]

The best alternative to using arrays is Vectors ...you should quit this.
Take a gander at here