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@mbostock
Last active Feb 9, 2016
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Randomized Depth-First IV
license: gpl-3.0
<!DOCTYPE html>
<meta charset="utf-8">
<style>
.link {
fill: none;
stroke: #000;
stroke-width: 1.5px;
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
var margin = {top: 20, right: 20, bottom: 20, left: 20},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var N = 1 << 0,
S = 1 << 1,
W = 1 << 2,
E = 1 << 3;
var root = generateTree(40, 40);
var tree = d3.layout.tree()
.size([height, width]);
var nodes = tree.nodes(root),
links = tree.links(nodes);
var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
svg.selectAll(".link")
.data(links)
.enter().append("path")
.attr("class", "link")
.attr("d", function(d) { return "M" + d.source.y + "," + d.source.x + "L" + d.target.y + "," + d.target.x; });
function generateTree(width, height) {
var cells = generateMaze(width, height), // each cell’s edge bits
visited = d3.range(width * height).map(function() { return false; }),
root = {index: cells.length - 1, children: []},
frontier = [root],
parent,
child,
childIndex,
cell;
while ((parent = frontier.pop()) != null) {
cell = cells[parent.index];
if (cell & E && !visited[childIndex = parent.index + 1]) visited[childIndex] = true, child = {index: childIndex, children: []}, parent.children.push(child), frontier.push(child);
if (cell & W && !visited[childIndex = parent.index - 1]) visited[childIndex] = true, child = {index: childIndex, children: []}, parent.children.push(child), frontier.push(child);
if (cell & S && !visited[childIndex = parent.index + width]) visited[childIndex] = true, child = {index: childIndex, children: []}, parent.children.push(child), frontier.push(child);
if (cell & N && !visited[childIndex = parent.index - width]) visited[childIndex] = true, child = {index: childIndex, children: []}, parent.children.push(child), frontier.push(child);
}
return root;
}
function generateMaze(width, height) {
var cells = new Array(width * height), // each cell’s edge bits
frontier = [];
var start = (height - 1) * width;
cells[start] = 0;
frontier.push({index: start, direction: N});
frontier.push({index: start, direction: E});
shuffle(frontier, 0, 2);
while (!exploreFrontier());
return cells;
function exploreFrontier() {
if ((edge = frontier.pop()) == null) return true;
var edge,
i0 = edge.index,
d0 = edge.direction,
i1 = i0 + (d0 === N ? -width : d0 === S ? width : d0 === W ? -1 : +1),
x0 = i0 % width,
y0 = i0 / width | 0,
x1,
y1,
d1,
open = cells[i1] == null; // opposite not yet part of the maze
if (d0 === N) x1 = x0, y1 = y0 - 1, d1 = S;
else if (d0 === S) x1 = x0, y1 = y0 + 1, d1 = N;
else if (d0 === W) x1 = x0 - 1, y1 = y0, d1 = E;
else x1 = x0 + 1, y1 = y0, d1 = W;
if (open) {
cells[i0] |= d0, cells[i1] |= d1;
var m = 0;
if (y1 > 0 && cells[i1 - width] == null) frontier.push({index: i1, direction: N}), ++m;
if (y1 < height - 1 && cells[i1 + width] == null) frontier.push({index: i1, direction: S}), ++m;
if (x1 > 0 && cells[i1 - 1] == null) frontier.push({index: i1, direction: W}), ++m;
if (x1 < width - 1 && cells[i1 + 1] == null) frontier.push({index: i1, direction: E}), ++m;
shuffle(frontier, frontier.length - m, frontier.length);
}
}
function shuffle(array, i0, i1) {
var m = i1 - i0, t, i, j;
while (m) {
i = Math.random() * m-- | 0;
t = array[m + i0], array[m + i0] = array[i + i0], array[i + i0] = t;
}
return array;
}
}
</script>
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