Thread: find largest in array with recrusion

Wrote this one to find largest integer in one dimensional array. It has to be done without global or local variables; only indexes of start & end + array itself.
Cannot get reasonable output & I'm not sure I have the right concept here, of using compression between array[pntrA] and *(++array).

Code:

int largest(int *array, int pntrA, int pntrB)
{
	if (pntrA==pntrB)
		return array[pntrA];

else
	if (pntrA<pntrB)
	{
		
			if (array[pntrA]<*(++array))
			{
				pntrA++;
			return largest(array, pntrA, pntrB);	
			}
		else 
			{
				*(++array)=array[pntrA];
				pntrA++;
				return largest(array, pntrA, pntrB);
			}
						
	}
	return 0;
}

Help will be highly appreciated

Assuming an unsorted array of course I would do something like this:

Code:

#include <stdio.h>

int largest(const int *, int, int);

int main(void)
{
  int arr[] = { 1, 8, 29, 3, 9, 23, 94, 2, 9};
  printf("Largest: %d\n", largest(arr, 0, (sizeof arr / sizeof arr[0]) - 1));
  return 0;
}

int largest (const int *arr, int low, int high)
{
  int mid, ret1, ret2;
  /* Since there is only one element it must be the highest */
  if ( low == high )
    return arr[low];

  /* Find the mid point of the array */
  mid = ((high - low) / 2) + low;
  /* Get the largest in the first half */
  ret1 = largest(arr, low, mid);
  /* Get the largest in the last half */
  ret2 = largest(arr, mid+1, high);
  /* Return the largest of the two values */
  return ret1 > ret2 ? ret1 : ret2;
}

The biggest problem I see with your code (besides formating) is that you have assignment statements that change the array. Since all you are doing is finding the largest value you should not change the values inside the array. To keep yourself from doing this change

Code:

int largest(int *array, int pntrA, int pntrB)

to

Code:

int largest(const int *array, int pntrA, int pntrB)

I think you were on the right track but it seems that you are assuming some type of sorting.

Mine works on unsorted arrays Just look at my test array

I'm gonna change mine to only take in two pointers

Well I'll be a.... Yeah ok when you sign up for that course save me a spot also

Oh one problem I've noticed with yours. It returns the position of the largest number where as the OP's code shows it returning the value.

In a much pretty and less user friendly package

Code:

int largest(int *arr, int l, int r)
{
  if ( l == r )
    return arr[l];

  return arr[l] > (r=largest(arr, l+1, r)) ? arr[l] : r;
}

I still want to do a binary search method for it. They said no local variables but made no mention of no inline asm

omg, prelude

I've think we had that happen once. The results weren't pretty.

Had I known before posting this problem, its going to be such a Fascinating duel...

Thank you both Prelude & Thantos!