How sort array in ascending order but put 0 at last?

Question

sort array in that manner that sorted array's member starts in ascending order but o value comes at last in c#

ulong[] arr = new ulong[30];

arr[0]=13325647855656;
arr[1]=65897426666332;
arr[2]=00685956265661;
arr[4]=0;

then output must be

arr[0]=00685956265661;
arr[1]=13325647855656;
arr[2]=65897426666332;
arr[4]=0;

Answer 1

you can use Linq OrderBy and ThenBy

ulong[] arr = new ulong[30];
arr[0] = 13325647855656;
arr[1] = 65897426666332;
arr[2] = 00685956265661;
arr[4] = 0;

var results = arr.OrderBy(x => x == 0).ThenBy(x => x);

Answer 2

You can use Array.Sort with this custom comparison delegate :

Array.Sort(arr, (u1, u2) =>
    {
        if (u1 == 0 && u2 == 0) return 0;
        else if (u1 == 0) return ulong.MaxValue.CompareTo(u2);
        else if (u2 == 0) return u1.CompareTo(ulong.MaxValue);
        else return u1.CompareTo(u2);
    });

Demo

If you want to use Linq ( ToArray() needs to create an additonal array internally), i would use:

arr = arr.OrderBy(x => x == 0).ThenBy(x => x).ToArray();

Answer 3

class ZeroIsBigComparer : System.Collections.Generic.IComparer<ulong>
    {
        public int Compare(ulong x, ulong y)
        {
            if (x == y) return 0;
            if (x == 0) return 1;
            if (y == 0) return -1;
            return x.CompareTo(y);
        }
    }

then

var comparer = new ZeroIsBigComparer();
arr = arr.OrderBy(x => x, comparer).ToArray();