2005-12-25 #1

// Author: Kevin Greer,   Date: Dec 25, 2005  --  Copyright 2005, All Rights Reserved
s = [[[[0,0,0],[0,7,1],[0,0,5]], [[5,0,0],[0,6,9],[0,7,1]], [[0,7,1],[8,5,3],[4,2,0]]], 
     [[[0,1,0],[0,0,2],[0,0,0]], [[7,8,0],[1,5,4],[0,9,2]], [[0,4,0],[3,6,0],[1,8,0]]],
     [[[0,6,4],[0,2,3],[0,5,0]], [[9,0,5],[0,1,0],[0,0,0]], [[7,0,0],[5,9,0],[0,0,0]]]]

function display() {
   for ( a = 0 ; a < 3 ; a++ ) {
	for ( b = 0 ; b < 3 ; b++ ) {
		for ( c = 0 ; c < 3 ; c++ ) {
			for ( d = 0 ; d < 3 ; d++ )
			    document.write(" " + s[a][c][b][d])
			if ( c < 2 ) document.write(" |")
		}
		document.write("<br/>")
	}
	if ( a < 2 ) document.write("-------+-------+-------<br/>")
   }
}
function solve(a, b, c, d) {
	if ( d == 3 ) return solve(a, b, c+1, 0)
	if ( c == 3 ) return solve(a, b+1, 0, 0)
	if ( b == 3 ) return solve(a+1, 0, 0, 0)
	if ( a == 3 ) return true
	if ( s[a][b][c][d] != 0 ) return solve(a, b, c, d+1)
	outer: for ( var j = 1 ; j <= 9 ; j++ ) {
		for ( var x = 0 ; x < 3 ; x++ ) for ( var y = 0 ; y < 3 ; y++ ) 
			if ( s[a][b][x][y] == j || s[a][x][c][y] == j || s[x][b][y][d] == j )
				continue outer
		s[a][b][c][d] = j
		if ( solve(a, b, c, d+1) ) return true
		s[a][b][c][d] = 0
	}
	return false
}

display()
document.write("<br/>solving...<br/><br/>")
if ( solve(0,0,0,0) ) display()