Self Excluding Product

The Fake Geek's blog: Self Excluding Product

 * Implement a method which takes an integer array and returns an integer array (of equal size) in
 * which each element is the product of every number in the input array with the exception of the
 * number at that index.
 *
 * Example:
 *   [3, 1, 4, 2] => [8, 24, 6, 12]
 */
public int[] selfExcludingProduct(int[] input) {
    // implementation...
}

 public int[] selfExcludingProduct (int[] input) {

  if (input == null)

   throw new NullPointerException ("Null input array!");

  int[] productArray = new int[input.length];

  if (input.length == 0)

   return productArray;

  int product = 1;

  int numOfZeros = 0;

  for (int i = 0; i < input.length; i++) {

   if (input[i] != 0)

    product *= input[i];

   else

    numOfZeros++;

   if (numOfZeros >= 2) {

    return productArray;

   }

  }

  for (int i = 0; i < input.length; i++) {

   if (numOfZeros == 0) {

    productArray[i] = product / input[i];

   }

   else {

    if (input[i] == 0)

     productArray[i] = product;

    else

     productArray[i] = 0;

   }

     

  }

   

  return productArray;

    

 }

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