Most of the mergesort implementations I see are similar to this. intro to algorithms book along with online implentations I search for. My recursion chops don't go much further than messing with Fibonacci generation (which was simple enough) so maybe it's the multiple recursions blowing my mind, but I can't even step through the code and understand whats going on even before I even hit the merge function.
How is it stepping through this? Is there some strategy or reading I should undergo to better understand the process here?
void mergesort(int *a, int*b, int low, int high)
{
int pivot;
if(low<high)
{
pivot=(low+high)/2;
mergesort(a,b,low,pivot);
mergesort(a,b,pivot+1,high);
merge(a,b,low,pivot,high);
}
}
and the merge(although frankly I'm mentally stuck before I even get to this part)
void merge(int *a, int *b, int low, int pivot, int high)
{
int h,i,j,k;
h=low;
i=low;
j=pivot+1;
while((h<=pivot)&&(j<=high))
{
if(a[h]<=a[j])
{
b[i]=a[h];
h++;
}
else
{
b[i]=a[j];
j++;
}
i++;
}
if(h>pivot)
{
for(k=j; k<=high; k++)
{
b[i]=a[k];
i++;
}
}
else
{
for(k=h; k<=pivot; k++)
{
b[i]=a[k];
i++;
}
}
for(k=low; k<=high; k++) a[k]=b[k];
}