Thread: Sorting 2Dimensional Array....

You start with this
T array[SIZE];
Where T is your type.

The call to qsort is
qsort( array, SIZE, sizeof(array[0]), compareFunction );

Now the compare function receives two T* pointers, initially cast to void*,
So typically, we have

Code:

int compareFunction ( const void *a, const void *b ) {
  const T* pa = a;
  const T* pb = b;
  // now compare pa->member with pb->member (for a struct)
  // or *pa and *pb for a scalar value
}

Doesn't matter, arrays are contiguous.

Code:

int test[][3] = {{3,5,1}, {5,2,3}, {19,14,5}};

qsort(test, sizeof(test) / sizeof(test[0][0]), sizeof(test[0][0]), myCompare);

Can also be written as,

Code:

int test[] = {3, 5, 1, 5, 2, 3, 19, 14, 5};

qsort(test, sizeof(test) / sizeof(test[0]), sizeof(test[0]), myCompare);

>I want to know what is the behaviour of this function, Why it is so giving unregular results???
You mean qsort()? It's not. Do a man qsort if you want to know how it works.

Originally Posted by zacs7

Doesn't matter, arrays are contiguous.

Code:

int test[][3] = {{3,5,1}, {5,2,3}, {19,14,5}};

qsort(test, sizeof(test) / sizeof(test[0][0]), sizeof(test[0][0]), myCompare);

Can also be written as,

Code:

int test[] = {3, 5, 1, 5, 2, 3, 19, 14, 5};

qsort(test, sizeof(test) / sizeof(test[0]), sizeof(test[0]), myCompare);

>I want to know what is the behaviour of this function, Why it is so giving unregular results???
You mean qsort()? It's not. Do a man qsort if you want to know how it works.

Actually i think the results of that wouldnt be what he wants.

Lets say the data looks like this:

Code:

int test[][3] = {
   {8, 2, 5},
   {0, 7, 2},
   {99, 5, 33}
};

I think the results would look like this:

Code:

int test[][3] = {
  {0, 2, 2},
  {5, 5, 7},
  {8, 33, 99}
};

But he may want the results to look like this:

Code:

int test[][3] = {
   {2, 5, 8},
   {0, 2, 7},
   {5, 33, 99}
};

Either way he has the basis to do both, by himself.

Code:

qsort(test[0], sizeof(test[0]) / sizeof(test[0][0]), sizeof(test[0][0]), myCompare); 
qsort(test[1], sizeof(test[1]) / sizeof(test[1][0]), sizeof(test[1][0]), myCompare);   /* 1s changed everywhere to show meaning */

/* ... */

And so on and so forth maybe?

Perhaps a loop?

Code:

for(i = 0; i < (sizeof(test) / sizeof(*test)); i++)
{
    qsort(test[i]... blah blah blah
}

In other words: you can look at the problem as sorting a bunch of 1D arrays. Simply step through the elements in the array to get 1D arrays that you can sort . . . .