Find the smallest number present in two arrays

SmallestNumberInTwoArrays.cs

class Program
{
    static void Main(string[] args)
    {
        var arr1 = new int[] { 10, 12, 5, 6, 3 };
        var arr2 = new int[] { 1, 9, 4, 8, 2, 3 };

        var arr1Sort = new int[] { 5, 8, 9, 13 };
        var arr2Sort = new int[] { 6, 7, 10, 11, 12, 13 };

        Console.WriteLine(FindSmallestNotSorted(arr1, arr2));

        Console.WriteLine(FindSmallestSorted(arr1Sort, arr2Sort));
    }

    static int FindSmallestNotSorted(int[] arr1, int[] arr2)
    {
        //O(n^2)
        //var result = -1;

        //for(var i = 0; i< arr1.Length; i++)
        //{
        //    for (var j = 0; j < arr2.Length; j++)
        //    {
        //        if(arr1[i] == arr2[j])
        //        {
        //            if (result == -1 || result > arr1[i])
        //            {
        //                result = arr1[i];
        //                break;
        //            }
        //        }
        //    }

        //}

        //return result;


        //O(n log n)
        Array.Sort(arr1);
        Array.Sort(arr2);

        return FindSmallestSorted(arr1, arr2);
    }

    //O(n)
    static int FindSmallestSorted(int[] arr1, int[] arr2)
    {
        var idx1 = 0;
        var idx2 = 0;

        while(idx1 < arr1.Length && idx2 < arr2.Length)
        {
            if (arr1[idx1] > arr2[idx2])
            {
                idx2++;
                continue;
            }

            if (arr1[idx1] < arr2[idx2])
            {
                idx1++;
                continue;
            }

            return arr1[idx1];
        }

        return -1;
    }
}