C - How can I sort and print an array in a method but have the prior unsorted array not be affected

Question

This is for a Deal or No Deal game.

So in my main function I'm calling my casesort method as such:

casesort(cases);

My method looks like this, I already realize it's not the most efficient sort but I'm going with what I know:

void casesort(float cases[10])
{
int i;
int j;
float tmp;
float zero = 0.00;

for (i = 0; i < 10; i++)
{
    for (j = 0; j < 10; j++)
    {
        if (cases[i] < cases[j])
        {
            tmp = cases[i];
            cases[i] = cases[j];
            cases[j] = tmp;
        }
    }
}

//Print out box money amounts
printf("\n\nHidden Amounts: ");
for (i = 0; i < 10; i++)
{
    if (cases[i] != zero)
        printf("[$%.2f] ", cases[i]);
}

}

So when I get back to my main it turns out the array is sorted. I thought void would prevent the method returning a sorted array. I need to print out actual case numbers, I do this by just skipping over any case that is populated with a 0.00. But after the first round of case picks I get "5, 6, 7, 8, 9, 10" printing out back in my MAIN. I need it to print the cases according to what has been picked. I feel like it's a simple fix, its just that my knowledge of the specifics of C is still growing. Any ideas?

"How can I sort and print an array in a method but have the prior unsorted array not be affected" - you copy the array. — , Sep 18 '13 at 21:57

score 1 · Answer 1 · answered Sep 18 '13 at 21:57

Return type void has nothing to do with prevention of array from being sorted. It just says that function does not return anything.

You see that the passed array itself is affected because an array decays to a pointer when passed to a function. Make a copy of the array and then pass it. That way you have the original list.

score 0 · Answer 2 · answered Sep 18 '13 at 22:00

In C, arrays are passed by reference. i.e. they're passed as pointer to the first element. So when you pass cases into your function, you're actually giving it the original array to modify. Try creating a copy and sorting the copy rather than the actual array. Creating a copy wouldn't be bad as you have only 10 floats.

score 0 · Answer 3 · answered Sep 18 '13 at 22:00

Instead of rolling your own sort, consider using qsort() or std::sort() if you are actually using c++

There are 2 obvious solutions. 1) Make a copy of the array and sort the copy (easy, waste some memory, likely not a problem these days). 2) Create a parallel array of integers and perform an index sort, i.e., instead of sorting thing original, you sort the index and then dereference the array using the index when you want the sorted version, otherwise by the raw unsorted array.

score 0 · Answer 4 · answered Sep 18 '13 at 22:06

0

Well, make a local copy of you input and sort it. Something like this:

void casesort(float cases[10])
{
    float localCases[10];
    memcopy(localCases, cases, sizeof(cases));
    ...

Then use localCases to do your sorting.

answered Sep 18 '13 at 22:06

ChrisWue

18,612
4
58
83

score 0 · Answer 5 · edited May 23 '17 at 11:56

0

If you don't want the array contents to be affected, then you'll have to create a copy of the array and pass that to your sorting routine (or create the copy within the routine itself).

Arrays Are Different™ in C; see my answer here for a more detailed explanation.

edited May 23 '17 at 11:56

Community

1
1

answered Sep 18 '13 at 22:08

John Bode

119,563
19
122
198

C - How can I sort and print an array in a method but have the prior unsorted array not be affected

5 Answers5