; begin KiXgolfUDF
;
;!
Function S($o)
Dim $i, $, $k, $t, $x

; Create a loop for the maximum number of x-es. (There are 16 fields)
For $x = 0 to 16

	; empty the row, column and square arrays and add one dimension to the solution array for current encountered x.
	Redim $r[3], $c[3], $q[3], $s[3, 3, $x]
	
	;loop through each column
	For $i = 0 to 3

		;loop through each row
		For $ = 0 to 3

			; retrieve the field from the original array
			$t = $o[$i,$]

			; find the corresponding square.
			;  0 0  1 1
			;  0 0  1 1
			;  2 2  3 3
			;  2 2  3 3
		
			$k = iif($i<2,iif($<2,0,1),iif($<2,2,3))
		
			; fill the row with all variables on that row
			$r[$] = $r[$] + $t
			
			; fill the column with all variables in that column
			$c[$i] = $c[$i] + $t

			; fill the square with all variables in that square
			$q[$k] = $q[$k] + $t

			; fill the solution array with the current variable 
			$s[$i, $, $x] = $t
		Next
	Next

	; if there are no more x-es in the rows, exit the function
	if instr(join($r),x)=0
		exit
	endif
	
	For $i = 0 to 3
		For $ = 0 to 3
				$k=@
				
				; Loop through each possible number (1,2,3 or 4)
				for $t = 1 to 4
					; If current variable is an x and the number ($t) does not exist in the corresponding row, column or square, add it to the variable $k 

					if instr($c[$i]+$r[$]+$q[iif($i<2,iif($<2,0,1),iif($<2,2,3))],$t)=0 & $o[$i,$]=x
						$k=$k+$t
					endif
				next

				; If there's only one digit in the variable $k, this means that that's the only solution for that x, so we can change that field in the initial array.
				if ($k^)=1
					$o[$i,$]=$k
					
					; we reset the $i and $j so that we exit these loops and start at the beginning of the $x loop again.
					$i=3 $=3
EndFunction
;!
;!
; end KiXgolfUDF