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jsmaze5.html
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<?xml-stylesheet href="#maze-style" type="text/css"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Maze</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<style type="text/css" id="maze-style">
body, div, table, tr, th, td { margin: 0; padding: 0; border: 0; }
div#wrap { width: 90vw; min-height: 90vh; padding: 10px; margin: auto auto; background: white; }
table.maze { width: 100%; height: 100%; border: none;}
table.maze td { border-width: 1px; border-style: solid; border-color: black; }
table.maze td { padding: 0; font-size: 12px; height: 1em; min-width: 1em; background-repeat: no-repeat; background-position: center; background-origin: padding-box; background-clip: padding-box; background-size: 50%;}
table.maze tr:first-child td { border-top-width: 2px; }
table.maze tr td:first-child { border-left-width: 2px; }
table.maze tr:last-child td { border-bottom-width: 2px; }
table.maze tr td:last-child { border-right-width: 2px; }
table.maze td.b0000 { border-top: none; border-right: none; border-bottom: none; border-left: none; }
table.maze td.b0001 { border-right: none; border-bottom: none; border-left: none; }
table.maze td.b0010 { border-top: none; border-bottom: none; border-left: none; }
table.maze td.b0011 { border-bottom: none; border-left: none; }
table.maze td.b0100 { border-top: none; border-right: none; border-left: none; }
table.maze td.b0101 { border-right: none; border-left: none; }
table.maze td.b0110 { border-top: none; border-left: none; }
table.maze td.b0111 { border-left: none; }
table.maze td.b1000 { border-top: none; border-right: none; border-bottom: none; }
table.maze td.b1001 { border-right: none; border-bottom: none; }
table.maze td.b1010 { border-top: none; border-bottom: none; }
table.maze td.b1011 { border-bottom: none; }
table.maze td.b1100 { border-top: none; border-right: none; }
table.maze td.b1101 { border-right: none; }
table.maze td.b1110 { border-top: none; }
table.maze td.b1111 { }
table.maze td.current { background-color: cyan; }
table.maze td.backtrack_0 { background-image: url(images/arrow-up.svg); }
table.maze td.backtrack_1 { background-image: url(images/arrow-right.svg); }
table.maze td.backtrack_2 { background-image: url(images/arrow-down.svg); }
table.maze td.backtrack_3 { background-image: url(images/arrow-left.svg); }
table.maze td.testing { background-image: url(images/question-lg.svg); }
</style>
<script type="text/javascript">
// <![CDATA[
// This function will add an onload handler to the body. It's fine to
// add a bunch of handlers, this keeps track of all of them.
function add_body_onload(func) {
var old_body_onload=window.onload;
window.onload=function() {
if (old_body_onload) { old_body_onload(); }
func();
}
}
// Get query parameters from the url. This returns an object like this:
// ?param => args['param']=true
// ?param=value => args['param']=value
// ?param[]=value => args['param']=[value,...]
function get_args() {
var args = new Object();
var query_string=location.search.slice(1);
if (!query_string) return args;
var query_pairs = query_string.split('&');
var pname, pvalue;
for (var i=0 ; i<query_pairs.length ; i++) {
var equal_position=query_pairs[i].indexOf('=');
if (equal_position<0) {
args[my_uri_decoder(query_pairs[i])]=true;
} else {
pname=my_uri_decoder(query_pairs[i].slice(0,equal_position));
pvalue=my_uri_decoder(query_pairs[i].slice(equal_position+1));
// If a name is followed by [], then we'll create an array of
// values. This is good for a multiple-select box
if (pname.match(/\[\]$/)) {
pname=pname.slice(0,-2);
if (!args[pname]) args[pname]=new Array();
args[pname].push(pvalue);
} else {
args[pname]=pvalue;
}
}
}
return args;
}
function my_uri_decoder(v) {
return decodeURIComponent(v.replace(/\+/g,'%20'));
}
var args=get_args();
// Basically, this array "converts" any number 0-15 to its
// binary equivalent as a string, which is useful for the use
// with the above stylesheet.
var to_bin=['0000', '0001', '0010', '0011', '0100', '0101', '0110', '0111', '1000', '1001', '1010', '1011', '1100', '1101', '1110', '1111'];
// Dir: 0 1 2 3
// N E S W
var deltax=[0,1,0,-1];
var deltay=[-1,0,1,0];
var reverse_dirs=[2,3,0,1];
// walls are horizontal or vertical
var wall_offsets={
h: { x: [0,0,0,0], y: [0,0,1,0] },
v: { x: [0,1,0,0], y: [0,0,0,0] }
};
var wall_types=['h','v','h','v'];
// perms array has these indices:
// 1. direction of entering square
// 2. a perm #
// 3. a direction #
// 4. sequence #
//
// Note that the perm# is broken down as follows:
// 0 - go straight first
// 1 - go straight second
// 2 - go straight last
//
// Direction # is:
// 0 - left first
// 1 - right first
//
// Therefore:
//
// 0,0 - straight,right,left
// 0,1 - straight,left,right
// 1,0 - right,straight,left
// 1,1 - left,straight,right
// 2,0 - right,left,straight
// 2,1 - left,right,straight
var perms = [[[[0,1,3],[0,3,1]],[[1,0,3],[3,0,1]],[[1,3,0],[3,1,0]]],
[[[1,2,0],[1,0,2]],[[2,1,0],[0,1,2]],[[2,0,1],[0,2,1]]],
[[[2,3,1],[2,1,3]],[[3,2,1],[1,2,3]],[[3,1,2],[1,3,2]]],
[[[3,0,2],[3,2,0]],[[0,3,2],[2,3,0]],[[0,2,3],[2,0,3]]]];
var xsize=parseInt(args['xsize']);
var ysize=parseInt(args['ysize']);
if (!xsize) xsize=10;
if (!ysize) ysize=10;
var right_preference=args['r'];
if (right_preference) {
right_preference = parseFloat(right_preference);
} else {
right_preference = 0.5;
}
if (right_preference<0.0) {
right_preference=0.0;
} else if (right_preference>1.0) {
right_preference=1.0;
}
var straight_preference=args['s'];
if (straight_preference) {
straight_preference = parseFloat(straight_preference);
} else {
straight_preference = 0.0;
}
if (straight_preference<-1.0) {
straight_preference=-1.0;
} else if (straight_preference>1.0) {
straight_preference=1.0;
}
var show_backtracks=args['b'];
// For each cell, we need to keep state. Walls are booleans,
// and consist of horizontal walls and vertical walls. We can
// determine which walls belong to a cell using wall_offsets
// and wall_types.
// For each cell position we'll keep the following information:
// 1. entry direction
// 2. permutation
// 3. current sequence
// 4. depth
// Only depth needs to be kept in an array for later use
var depths = new Array(xsize);
var backtracks = new Array(xsize);
var walls = { h: new Array(xsize), v: new Array(xsize+1) }
var startx=0;
var starty=ysize-1;
var maxdepth=0;
// If performed recursively, this algorithm is simple...
function make_maze(x,y,depth,dir) {
// remove the wall where we entered
remove_wall(x,y,reverse_dirs[dir]);
// record backtracking
backtracks[x][y] = reverse_dirs[dir];
// update max depth
if (depth>maxdepth) maxdepth=depth;
depths[x][y]=depth;
var i,j,k,new_dir,straightness;
var lr=(Math.random()>=right_preference ? 0 : 1);
// straightness is a number from 0 to 2, with "0" being
// straight first, "1" straight second, and "2" straight
// last. straight_preference is between -1 and 1, with
// -1 being very straight, 0 being neutral, and 1 being
// very curvy. We'll use the beta function to come up
// with some numbers for this.
if (straight_preference < 0.0) {
straightness=get_straightness(-straight_preference);
} else if (straight_preference > 0.0) {
straightness=2-get_straightness(straight_preference);
} else {
straightness=Math.floor(Math.random()*2.999999);
}
for (new_dir of perms[dir][straightness][lr]) {
i=x+deltax[new_dir];
j=y+deltay[new_dir];
if (in_bounds(i,j) && unvisited(i,j)) {
make_maze(i,j,depth+1,new_dir);
}
}
}
function in_bounds(x,y) {
return (x>=0 && x<xsize && y>=0 && y<ysize);
}
function four_walls(x,y) {
var ret = new Array(4);
for (var dir=0; dir<4; dir++) {
ret[dir] = get_wall(x,y,dir);
}
return ret;
}
function four_walls_as_integer(x,y) {
var ret = 0;
var fw_arr = four_walls(x,y);
for (var dir=0; dir<4; dir++) {
if (fw_arr[dir]) ret |= 1<<dir;
}
return ret;
}
function unvisited(x,y) {
return four_walls(x,y).every(t => t);
}
function get_wall(x,y,dir) {
wall_type = wall_types[dir];
return walls[wall_type][x+wall_offsets[wall_type]['x'][dir]][y+wall_offsets[wall_type]['y'][dir]];
}
function set_wall(x,y,dir,val) {
wall_type = wall_types[dir];
walls[wall_type][x+wall_offsets[wall_type]['x'][dir]][y+wall_offsets[wall_type]['y'][dir]] = val;
}
function remove_wall(x,y,dir) {
set_wall(x,y,dir,false);
}
// seed is 0 -> 1. At 0, we have a regular distribution and at 1
// we have a distribution completely weighted toward 0. Simply, at
// 0 the cutoffs are at 1/3 and 2/3, since 2/3 is half way between
// 1/3 and 1. At .5, the first cutoff is 2/3 and the second is
// 11/12.
// cutoff2 is .5 of remaining space when seed is 0 and 0 of
// remaining space when seed is 1.
function get_straightness(seed) {
var cutoff1 = .333333333 + seed*.666666666
var rnd = Math.random();
if (rnd<cutoff1) {
return 0;
} else {
var cutoff2 = 1.0 - (1.0 - cutoff1) * (.5-seed*.5);
if (rnd<cutoff2) {
return 1;
} else {
return 2;
}
}
}
function test_get_straightness() {
var counts = new Array(11);
for (var seed=0; seed<=10; seed++) {
these_counts = [0,0,0];
for (var x=0; x<50000; x++) {
var straightness = get_straightness(seed/10.0);
these_counts[straightness] += 1;
}
counts[Math.floor(seed)] = these_counts;
}
console.log(counts);
}
function create_table_cells(table, xsize, ysize) {
for (var y=0; y<ysize; y++) {
var tr = document.createElement('tr');
tr.id = 'row_' + y;
tr.className = 'row_' + y;
for (var x=0; x<xsize; x++) {
var td = document.createElement('td');
td.id = 'cell_' + x + '_' + y;
td.className = 'b1111 row_' + y + ' col_' + x;
tr.appendChild(td);
}
table.appendChild(tr);
}
}
function display_maze(table, xsize, ysize, walls, backtracks, depths) {
for (var x=0; x<xsize; x++) {
for (var y=0; y<ysize; y++) {
var td = document.getElementById('cell_' + x + '_' + y);
td.classList.add('b' + to_bin[four_walls_as_integer(x,y)]);
if (show_backtracks) {
td.classList.add('backtrack_' + backtracks[x][y]);
}
}
}
}
function init() {
maxdepth=0;
for (var x=0 ; x<xsize ; x++) {
depths[x] = new Array(ysize);
}
for (var x=0 ; x<xsize ; x++) {
backtracks[x] = new Array(ysize);
}
// Create the horizontal walls, all set to "true"
for (var x=0 ; x<xsize ; x++) {
walls['h'][x] = new Array(ysize+1);
for (var y=0 ; y<ysize+1 ; y++) {
walls['h'][x][y] = true;
}
}
// Create the vertical walls, all set to "true"
for (var x=0 ; x<xsize+1 ; x++) {
walls['v'][x] = new Array(ysize);
for (var y=0 ; y<ysize ; y++) {
walls['v'][x][y] = true;
}
}
var table = document.getElementById('maze');
create_table_cells(table, xsize, ysize);
make_maze(startx,starty,0,0);
// open walls for start/end
walls['h'][xsize-1][0] = false;
display_maze(table, xsize, ysize, walls, backtracks, depths);
}
add_body_onload(init);
//]]>
</script>
</head>
<body>
<div id="wrap">
<p>
This is a more modern rewrite of the recursive backtracker set
in a square grid using an HTML table for display. Parameters
are xsize, ysize, b to show backtracking, l for left/right
preference (0 left, 1 right), and s for straightness preference
(-1 really straight, 0 normal, 1 really curvy).
</p>
<table id="maze" class="maze" cellspacing="0">
</table>
</div>
</body>
</html>