Using a pointer for selection sort

Question

I am trying to use a pointer for an array for selection sort.

void sort(int size, int *ptr)
{
int temp;
bool swap;
do
{
    swap = false;
    for (int count = 0; count < (size - 1); count++)
    {
        if (*ptr[count] > *ptr[count + 1])
        {
            temp = *ptr[count];
            *ptr[count] = *ptr[count + 1];
            *ptr[count + 1] = temp;
            swap = true;
        }
    }
} while (swap);
}

im getting a lot of errors saying illegal direction because when using * it must be a pointer. I use it in other methods fine its just this one that it has trouble. This is the call im using.

sort(arraySize, numArray);

everything is declared and working in other methods.

which lines are you seeing error messages? also it probably should be ptr[count] and not *ptr[count]. ptr is a pointer and not an array of pointers. — Richard Chambers
– Richard Chambers, Commented Feb 10, 2015 at 5:04
So change *ptr[count] to just ptr[count]. You do not need to dereference a pointer if you are using array subscript. Pointers can be dereferenced with either the * operator or with an array subscript in most cases. — Richard Chambers
– Richard Chambers, Commented Feb 10, 2015 at 5:10
This looks like a bubble sort, not a selection sort. For a selection sort, you'd walk through the array just looking at the elements to find the smallest (not swapping anything yet). Then, when you got to the end of the array so you had found the smallest element in the unsorted part of the array, you'd do one swap from there to the first unsorted spot (and then have one more item sorted). — Jerry Coffin
– Jerry Coffin, Commented Feb 10, 2015 at 5:10
@BucketsOstuff please consider simple errors such as missing semicolon. There should not be any excuse for posting with such mistakes. — Doonyx
– Doonyx, Commented Feb 10, 2015 at 5:15

Rupesh Yadav. · Accepted Answer · 2015-02-10 05:11:09Z

1

use ptr[] instead of *ptr[] because, ptr is pointer and if used with [] then it returns element at that location like array does.

void sort(int size, int *ptr)
{
int temp;
bool swap;
do
{
    swap = false;
    for (int count = 0; count < (size - 1); count++)
    {
        if (ptr[count] > ptr[count + 1])
        {
            temp = ptr[count];
            ptr[count] = ptr[count + 1];
            ptr[count + 1] = temp;
            swap = true;
        }
    }
} while (swap);
}

answered Feb 10, 2015 at 5:11

Rupesh Yadav.

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Comments

spin_eight · Accepted Answer · 2015-02-10 05:10:10Z

0

error is in *ptr[count] this is wrong syntax for a pointer dereferencing.

Do ptr[count] or *(ptr + count)

answered Feb 10, 2015 at 5:10

spin_eight

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Comments

Doonyx · Accepted Answer · 2015-02-10 05:10:46Z

0

Here's the compilation errors removed version.

void sort(int size, int *ptr)
{
int temp;
bool swap;
do
{
    swap = false;
    for (int count = 0; count < (size - 1); count++)
    {
        if (ptr[count] > ptr[count + 1])
        {
            temp = ptr[count];
            ptr[count] = ptr[count + 1];
            ptr[count + 1] = temp;
            swap = true;
        }
    }
} while (swap);
}

answered Feb 10, 2015 at 5:10

Doonyx

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Comments

Community · Accepted Answer · 2017-05-23 10:24:16Z

0

read also: C++ Using pointers for selection sort function

for more examples: http://www.codemiles.com/c-examples/c-selection-sort-t2916.html

*ptr[count] doesn't mean anything

ptr - pointer *ptr - value - dereferenced

edited May 23, 2017 at 10:24

CommunityBot

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answered Feb 10, 2015 at 5:11

azbarcea

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Comments

Usama Khan · Accepted Answer · 2015-02-10 05:25:15Z

0

This is the correct structure You must not use * while using the pointer notation of an array, the use of pointer name without '*' itslef refers to the 0 index of pointer array

void sort(int size, int *ptr)
{
int temp;
bool swap;
do
{
    swap = false;
    for (int count = 0; count < (size - 1); count++)
    {
        if (ptr[count] > ptr[count + 1])
        {
            temp = ptr[count];
            ptr[count] = ptr[count + 1];
            ptr[count + 1] = temp;
            swap = true;
        }
    }
} while (swap);
}

answered Feb 10, 2015 at 5:25

Usama Khan

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