对对象数组的选择排序

Question

Looked around online, but haven't been able to find anything concerning this. I'm in a C++ introductory class and have a project that is dealing with Arrays of Objects. An object (called media) has a name and a rating. I have three different media objects put into an media object array. I need to find a way to sort them by name. I was given code for selection sort for c-strings, but haven't been able to figure out what exactly to do with this to change it over to dealing with the media objects. Here is my selection sort for the c-strings.

void selectsort(char str[][20], int N)
{
int pass, j, min;
char temp[20];
for (pass = 0; pass <= N - 2; pass++)  // passes
{
min = pass;
for (j = pass + 1; j < N; j++)  // in each pass
if (strcmp(str[min], str[j]) > 0)
min = j;
    strcpy(temp, str[min]);
    strcpy(str[min], str[pass]);
    strcpy(str[pass], temp);
    }
}

I have gotten rid of strcmp by overloading < with

int media::operator<(media med)
    {
        return strcmp(mname, med.mname);
    }

and strcpy by overloading = with

void media::operator=(media med)
    {
        strcpy(mname, med.mname);
    }

I believe that this would return the same results, yes?

So here is my code so far (have just been throwing myself at it non-understanding of how to do it).

void selsort(media mry[], int n) // mry[] is the object array, n is the 
                                 // number of objects in the array
{
    int pass, j, min;
    media temp[1];
    for (pass = 0; pass <= n - 2; pass++)  // passes
    {
        min = pass;
        for (j = pass + 1; j < n; j++)  // in each pass
            if ((mry[min] < mry[j]) < 0)
                min = j;
        temp = mry[min];
        mry[min] = mry[pass];
        temp = mry[min];
    }
}

I understand that there are a lot of flaws in this code. The temp comparison doesn't work and when I try to get it to using *temp or temp[0] (trying everything under the sun over here) I get corrupted data errors. I can't seem to figure it out though. I've always struggled with understanding sorts, and this just adds insult to injury. (Also please note that some notations might not be correct, but this is what I was taught in this class and what this professor asks that we code in)

Thanks for any help!

Answer 1

There are 2 things wrong with your code:

1. media temp[1]; Why would you want your temporary media storage for swapping be an array of 1?
2. The swapping: temp = mry[min]; mry[min] = mry[pass]; temp = mry[min]; temp = mry[min]; mry[min] = mry[pass]; temp = mry[min]; See anything wrong with it?

Here is the adjusted function, which BTW works fine:

void selsort(media mry[], int n) // mry[] is the object array, n is the 
                                 // number of objects in the array
{
    int pass, j, min;
    media temp;
    for (pass = 0; pass <= n - 2; pass++)  // passes
    {
        min = pass;
        for (j = pass + 1; j < n; j++)  // in each pass
            if ((mry[min] < mry[j]) < 0)
                min = j;
        temp = mry[min];
        mry[min] = mry[pass];
        mry[pass] = temp;
    }
}