You're given a list of n integers arr[0..(n-1)]. You must compute a list output[0..(n-1)] such that, for each index i (between 0 and n-1, inclusive), output[i] is equal to the product of the three largest elements out of arr[0..i] (or equal to -1 if i < 2, as arr[0..i] then includes fewer than three elements).
Note that the three largest elements used to form any product may have the same values as one another, but they must be at different indices in arr.
Signature
int[] findMaxProduct(int[] arr)
Input
n is in the range [1, 100,000].
Each value arr[i] is in the range [1, 1,000].
Output
Return a list of n integers output[0..(n-1)], as described above.
Example 1
n = 5
arr = [1, 2, 3, 4, 5]
output = [-1, -1, 6, 24, 60]
The 3rd element of output is 321 = 6, the 4th is 432 = 24, and the 5th is 543 = 60.
Example 2
n = 5
arr = [2, 1, 2, 1, 2]
output = [-1, -1, 4, 4, 8]
The 3rd element of output is 221 = 4, the 4th is 221 = 4, and the 5th is 222 = 8.

My simple C# solution below:

	public static int[] FindMaxProduct(int[] input)
        {
            var ansArr = new int[input.Length];
            var firstLargetst = input[0];
            var secondLargetst = input[1];
            ansArr[0] = ansArr[1] = -1;
            for (int i = 2; i < input.Length; i++)
            {
                ansArr[i] = firstLargetst * secondLargetst * input[i];
                if (firstLargetst < input[i] && firstLargetst < secondLargetst)
                {
                    firstLargetst = input[i];
                    continue;
                }
                if (secondLargetst < input[i] && secondLargetst < firstLargetst)
                {
                    secondLargetst = input[i];
                }
            }
            return ansArr;
        }