Thread: bubble sort with pointers not working

In every step, you are supposed to start in the opposite end of the array from where your "master" loops index starts and then work your way to what the index currently is. So in your case you should be sorting from the end to the beginning.

Also, you are supposed to compare the element you are currently on with the next one according to the direction in which you are looping(which should be backwards in your case), not with the one situated farthest to the end / beginning.

Code:

#include <iostream>
using namespace std;

const int ELEMENTS = 4;

int main()
{
	int num[4];
	int n;
	int i; 
	int j;
	int temp;
	int *Ptr = NULL;
	
	for(n = 0; n < ELEMENTS; n++)
	{
		cout << "Type a number: ";
		cin >> num[n];
	}

	Ptr = num;
	for(i = 0; i < ELEMENTS; i++)

		for(j = ELEMENTS - 1; j > i; j--)
			if(*(Ptr + j) < *((Ptr + j) - 1))
			{
				temp = num[j];
				*(Ptr + j) = *((Ptr + j) - 1);
				*((Ptr + j) -1)= temp;
			}
	for(i = 0; i < 4; i++)
		cout << num[i] << endl;

	return 0;
}

That sorts the array just fine, but for consistency you might want to change

Code:

temp = num[j];

to

Code:

temp = *(Ptr + j);

And the indentation is a bit wrong in the end, it should be like in the above code.

edit: pianorain's find

Code:

const int ELEMENTS = 4;

int main()
{
    int num[4];
    <snip>

    for(j = ELEMENTS; j > i; j--)
        if(*(Ptr + j) < *((Ptr + j) - 1))
        {
            temp = num[j];
            <snip>
        }
}

See a problem here? I'll give you a hint...num[4] doesn't exist.

Why are you using an extra pointer to begin with? It doesn't add any functionality. The whole program can be rewritten without it. Also, just to keep your array bounds consistent, you might want to declare your integer array as num[ELEMENTS].