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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| body { | |
| background: #000; | |
| } | |
| </style> | |
| <body> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500, | |
| cellSize = 4, | |
| cellWidth = Math.ceil(width / cellSize), | |
| cellHeight = Math.ceil(height / cellSize); | |
| var canvas = d3.select("body").append("canvas") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var context = canvas.node().getContext("2d"); | |
| context.fillStyle = "white"; | |
| var maze = d3.range(cellHeight * cellWidth).map(function() { return 1; }), | |
| frontier = []; | |
| addToMaze(1, cellHeight - 2); | |
| addToFrontier(2, cellHeight - 2); | |
| addToFrontier(1, cellHeight - 3); | |
| d3.timer(function() { | |
| for (var i = 0; i < 100; ++i) { | |
| if (exploreFrontier()) { | |
| return true; | |
| } | |
| } | |
| }); | |
| function fillCell(i) { | |
| context.fillRect((i % cellWidth) * cellSize, (i / cellWidth | 0) * cellSize, cellSize, cellSize); | |
| } | |
| function clearCell(i) { | |
| context.clearRect((i % cellWidth) * cellSize, (i / cellWidth | 0) * cellSize, cellSize, cellSize); | |
| } | |
| function index(x, y) { | |
| return y * cellWidth + x; | |
| } | |
| function addToMaze(x, y) { | |
| var i = index(x, y); | |
| maze[i] = 0; | |
| fillCell(i); | |
| } | |
| function addToFrontier(x, y) { | |
| var i = index(x, y); | |
| if (!maze[i]) return; | |
| fillCell(i); | |
| frontier.push(i); | |
| } | |
| function removeFromFrontier() { | |
| if (!frontier.length) return null; | |
| var index = Math.random() * frontier.length | 0; | |
| var i = frontier[index]; | |
| frontier[index] = frontier[frontier.length - 1]; | |
| frontier.pop() | |
| clearCell(i); | |
| return i; | |
| } | |
| function exploreFrontier() { | |
| var i = removeFromFrontier(); | |
| if (i == null) return true; | |
| var x = i % cellWidth, | |
| y = i / cellWidth | 0, | |
| ox, | |
| oy, | |
| oi = x > 0 && !maze[index(x - 1, y)] ? (x < cellWidth - 1 ? index(ox = x + 1, oy = y) : NaN) | |
| : x < cellWidth - 1 && !maze[index(x + 1, y)] ? (x > 0 ? index(ox = x - 1, oy = y) : NaN) | |
| : y > 0 && !maze[index(x, y - 1)] ? (y < cellHeight - 1 ? index(ox = x, oy = y + 1) : NaN) | |
| : y < cellHeight - 1 && !maze[index(x, y + 1)] ? (y > 0 ? index(ox = x, oy = y - 1) : NaN) | |
| : NaN; | |
| if (maze[oi]) { // opposite cell is filled | |
| addToMaze(x, y); | |
| var inside = true; | |
| context.fillStyle = "magenta"; | |
| if (ox > 0) addToFrontier(ox - 1, oy); else inside = false; | |
| if (ox < cellWidth - 1) addToFrontier(ox + 1, oy); else inside = false; | |
| if (oy > 0) addToFrontier(ox, oy - 1); else inside = false; | |
| if (oy < cellHeight - 1) addToFrontier(ox, oy + 1); else inside = false; | |
| context.fillStyle = "white"; | |
| if (inside) addToMaze(ox, oy); | |
| } | |
| } | |
| </script> |
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