Merge two arrays and sort the final one

Question

In an interview I was asked the following question. I am given two arrays, both of them are sorted.

BUT

Array 1 will have few -1\'s and Array 2 will have to

Answer 1

Let me re-phrase three most important aspects of the task:

• Both arrays are sorted and include positive integers (except -1 place-holders in Array1)
• The -1 is meaningless placeholder (its position in Array1 is random)
• Array1 length equals output array length

Pseudo logic:

• parse both array1 and array2 from the first position to end of array
• ignore -1 values in array1
• if array1[current position] <= array2[current position] then write array1[current position] into merged array and move to next position in array1; otherwise apply same for array2

Code example:

            public static void AMerge()
        {
            int[] array1 = new int[] { 3, 6, -1, 11, 15, -1, 23, 34, -1, 42 };
            int[] array2 = new int[] { 1, 9, 28 };
            int[] arrayMerged = new int[array1.Length];

            int array1Index = 0;
            int array2Index = 0;

            for (int arrayMergedIndex = 0; arrayMergedIndex < array1.Length; arrayMergedIndex++)
            {
                while (array1[array1Index] == -1) array1Index++; //ignore -1 placeholders
                if ((array1Index < array1.Length && array2Index >= array2.Length) 
                    || array1[array1Index] <= array2[array2Index])  //choose which array will provide current merged value
                {
                    arrayMerged[arrayMergedIndex] = array1[array1Index];
                    array1Index++;
                }
                else
                {
                    arrayMerged[arrayMergedIndex] = array2[array2Index];
                    array2Index++;
                }
            }

            char[] charsToTrim = { ',', ' '};
            string arrayMergedString = "{";
            foreach (int f in arrayMerged) arrayMergedString += f.ToString() + " ";
            arrayMergedString = arrayMergedString.TrimEnd(charsToTrim) + "}";
            Console.WriteLine(arrayMergedString);
            Console.ReadKey();
        }
    }

Note:

• Optimizing for speed => creating new arrayMerged; optimization for space would require moving array1 elements in the else branch