28:null 29:["$","title",null,{"children":"Prim’s Algorithm IV | Mike Bostock | Observable"}] 2e:T4a0,cells = { const heap = new FlatQueue(); const cells = new Uint8Array(width * height); let edge; heap.push({index: 0, direction: N}, Math.random()); heap.push({index: 0, direction: E}, Math.random()); while (edge = heap.pop()) { let i0 = edge.index, i1; let d0 = edge.direction, d1; let x0 = i0 % width, x1; let y0 = i0 / width | 0, y1; if (d0 === N) i1 = i0 - width, x1 = x0, y1 = y0 - 1, d1 = S; else if (d0 === S) i1 = i0 + width, x1 = x0, y1 = y0 + 1, d1 = N; else if (d0 === W) i1 = i0 - 1, x1 = x0 - 1, y1 = y0, d1 = E; else i1 = i0 + 1, x1 = x0 + 1, y1 = y0, d1 = W; if (cells[i1] === 0) { cells[i0] |= d0, cells[i1] |= d1; if (y1 > 0 && cells[i1 - width] === 0) { heap.push({index: i1, direction: N}, Math.random()); } if (y1 < height - 1 && cells[i1 + width] === 0) { heap.push({index: i1, direction: S}, Math.random()); } if (x1 > 0 && cells[i1 - 1] === 0) { heap.push({index: i1, direction: W}, Math.random()); } if (x1 < width - 1 && cells[i1 + 1] === 0) { heap.push({index: i1, direction: E}, Math.random()); } } } return cells; }2f:[] 2c:{"id":"151ce7b77b6e3a17","slug":"prims-algorithm-iv","title":"Prim’s Algorithm IV","thumbnail":"c736d78badd2018d810d300474bcacead230a227b8fa10e7bec6edaeaf0ea2dc","access_level":"public","create_time":"$D2019-08-07T19:23:33.039Z","update_time":"$D2019-08-09T17:03:38.413Z","view_time":null,"first_public_time":"$D2019-08-07T19:43:06.150Z","has_unpublished_edits":null,"fork":false,"stars":7,"starred":false,"owner":{"type":"team","id":"8c2e47252fd4995c","login":"mbostock","name":"Mike Bostock","avatar_url":"https://avatars-next.observableusercontent.com/7dbba99ced40bd5ab8013c99b1a11da61231bce321ba1148a9d16ad0f121550a","tier":"pro_2026"},"version":82,"publish_version":82,"role":null,"authored":false,"authors":[{"type":"individual","id":"074c414ad1d825f5","login":"mbostock","name":"Mike Bostock","avatar_url":"https://avatars-next.observableusercontent.com/7dbba99ced40bd5ab8013c99b1a11da61231bce321ba1148a9d16ad0f121550a","tier":null}],"members":[{"type":"individual","id":"074c414ad1d825f5","login":"mbostock","name":"Mike Bostock","avatar_url":"https://avatars-next.observableusercontent.com/7dbba99ced40bd5ab8013c99b1a11da61231bce321ba1148a9d16ad0f121550a","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":8,"collection":null,"type":"notebook","body":{"title":"Prim’s Algorithm IV","cells":[{"id":0,"value":"md`# Prim’s Algorithm IV\n\nColor-cycling applied to a spanning tree generated by [Prim’s algorithm](/@mbostock/prims-algorithm).`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":14,"value":"canvas = {\n const context = DOM.context2d(width, height, 1);\n const image = context.createImageData(width, height);\n const pixels = new Uint32Array(image.data.buffer);\n context.canvas.style.imageRendering = \"pixelated\";\n while (true) {\n for (let i = 0, c, r = performance.now() / 30; i < n; ++i) {\n pixels[i] = colors[(c = Math.round(distance[i] / 3 - r) % 360) < 0 ? c + 360 : c];\n }\n context.putImageData(image, 0, 0);\n yield context.canvas;\n }\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":36,"value":"colors = new Uint32Array(new Uint8ClampedArray(Array.from({length: 360}, (_, i) => d3.rgb(d3.interpolateRainbow(i / 360))).flatMap(c => [c.r, c.g, c.b, 255])).buffer)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":26,"value":"distance = {\n const distance = new Array(n);\n let frontier = [(height - 1) * width];\n distance[frontier[0]] = 0;\n for (let d = 0; frontier.length; ++d) {\n let frontier1 = [];\n for (let i = 0, n0 = frontier.length; i < n0; ++i) {\n let i0 = frontier[i], i1;\n if (cells[i0] & E && distance[i1 = i0 + 1] === undefined) distance[i1] = d, frontier1.push(i1);\n if (cells[i0] & W && distance[i1 = i0 - 1] === undefined) distance[i1] = d, frontier1.push(i1);\n if (cells[i0] & S && distance[i1 = i0 + width] === undefined) distance[i1] = d, frontier1.push(i1);\n if (cells[i0] & N && distance[i1 = i0 - width] === undefined) distance[i1] = d, frontier1.push(i1);\n }\n frontier = frontier1;\n }\n return distance;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":63,"value":"$2e","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":15,"value":"N = 1 << 0","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":20,"value":"S = 1 << 1","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":19,"value":"W = 1 << 2","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":18,"value":"E = 1 << 3","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":22,"value":"n = width * height","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":8,"value":"height = 600","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":65,"value":"FlatQueue = require(\"flatqueue@1\")","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":39,"value":"d3 = require(\"d3-color@1\", \"d3-scale-chromatic@1\")","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W2f","stdlib":"1","titling":"auto"}} 2d:"$2c:body"