3354. Make Array Elements Equal to Zero

public class Solution
{
    public int CountValidSelections(int[] nums)
    {
        // Calculate the total sum of all elements in the array
        int totalSum = nums.Sum();

        // Initialize result counter and left sum accumulator
        int validCount = 0;
        int leftSum = 0;

        // Iterate through each element in the array
        foreach (int currentValue in nums)
        {
            if (currentValue != 0)
                // Add non-zero values to the left sum
                leftSum += currentValue;
            else
            {
                // At a zero position, check balance conditions

                // Perfect balance: left sum equals right sum
                // leftSum == totalSum - leftSum => 2 * leftSum == totalSum
                if (leftSum * 2 == totalSum)
                    // Both directions are valid when perfectly balanced
                    validCount += 2;
                // Near balance: difference between left and right is at most 1
                // |leftSum - rightSum| <= 1 => |leftSum - (totalSum - leftSum)| <= 1
                // => |2 * leftSum - totalSum| <= 1
                else if (Math.Abs(leftSum * 2 - totalSum) <= 1)
                    // One direction is valid when nearly balanced
                    validCount++;
            }
        }

        return validCount;
    }
}