2e:null 2f:["$","title",null,{"children":"🎄 Advent of Code 2022: Day 9 | Mike Bostock | Observable"}] 34:[{"id":"3e425ff2e1c5f48186b9dea30d41b8dd1cde53686e49a5575975d3a8402c2f7592a6beda7f4680e8ebb57b22cb73a952fcf289c1902e3a4e02de834d8cca6130","href":"https://static.observableusercontent.com/files/3e425ff2e1c5f48186b9dea30d41b8dd1cde53686e49a5575975d3a8402c2f7592a6beda7f4680e8ebb57b22cb73a952fcf289c1902e3a4e02de834d8cca6130","name":"input.txt","type":"text/plain","lastModified":1670563649410.885,"size":8355}] 32:{"id":"21b3949cdf458b8e","slug":"advent-of-code-2022-day-9","title":"🎄 Advent of Code 2022: Day 9","thumbnail":"35e7dbdc8cfde267c2e87671074005225b4300c8c5f043ddafc7df34865ec7ea","access_level":"public","create_time":"$D2022-12-09T04:56:57.717Z","update_time":"$D2022-12-09T06:14:27.604Z","view_time":null,"first_public_time":"$D2022-12-09T04:56:57.717Z","has_unpublished_edits":null,"fork":false,"stars":2,"starred":false,"owner":{"type":"team","id":"8c2e47252fd4995c","login":"mbostock","name":"Mike Bostock","avatar_url":"https://avatars-next.observableusercontent.com/7dbba99ced40bd5ab8013c99b1a11da61231bce321ba1148a9d16ad0f121550a","tier":"pro_2026"},"version":185,"publish_version":null,"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":2,"collection":{"id":"76221098c5a818c6","slug":"advent-of-code-2022","title":"🎄 Advent of Code 2022","owner":{"id":"8c2e47252fd4995c","login":"mbostock","name":"Mike Bostock"}},"type":"notebook","body":{"title":"🎄 Advent of Code 2022: Day 9","cells":[{"id":0,"value":"# 🎄 Advent of Code 2022: Day 9\n\nhttps://adventofcode.com/2022/day/9","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":5,"value":"test = `R 4\nU 4\nL 3\nD 1\nR 4\nD 1\nL 5\nR 2\n`","pinned":true,"hidden":true,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":16,"value":"testMotions = parseMotions(test)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":9,"value":"testInitialState = `......\n......\n......\n......\nH.....`","pinned":true,"hidden":true,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":13,"value":"function parseMotions(input) {\n return input.trim().split(\"\\n\").map(parseMotion);\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":19,"value":"function parseMotion(input) {\n let [direction, length] = input.split(/\\s+/);\n if (!/^[RULD]$/.test(direction)) throw new Error(`invalid direction: ${input}`);\n if (!Number.isInteger(length = +length)) throw new Error(`invalid length: ${input}`);\n return {direction, length};\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":34,"value":"[...processMotions(testMotions)]","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":31,"value":"function* processMotions(motions) {\n let x = 0;\n let y = 0;\n yield [x, y];\n for (const {direction, length} of motions) {\n switch (direction) {\n case \"L\": for (let i = 0; i < length; ++i) yield [--x, y]; break;\n case \"R\": for (let i = 0; i < length; ++i) yield [++x, y]; break;\n case \"U\": for (let i = 0; i < length; ++i) yield [x, ++y]; break;\n case \"D\": for (let i = 0; i < length; ++i) yield [x, --y]; break;\n }\n }\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":58,"value":"visualizeMotion(testMotions)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":70,"value":"function* processTailMotions(motions) {\n let tx = 0;\n let ty = 0;\n yield [tx, ty];\n for (const [hx, hy] of processMotions(motions)) {\n [tx, ty] = moveTail(tx, ty, hx, hy);\n yield [tx, ty];\n }\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":132,"value":"function moveTail(tx, ty, hx, hy) {\n if (tx < hx - 2 || tx > hx + 2 || ty < hy - 2 || ty > hy + 2) throw new Error(`head is too far away`);\n if (!(hx - 1 <= tx && tx <= hx + 1 && hy - 1 <= ty && ty <= hy + 1)) {\n tx += hx > tx ? 1 : hx < tx ? -1 : 0;\n ty += hy > ty ? 1 : hy < ty ? -1 : 0;\n }\n return [tx, ty];\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":93,"value":"function countDistinctPositions(positions) {\n return d3.union(Array.from(positions, (motion) => motion.join())).size;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":90,"value":"countDistinctPositions(processTailMotions(testMotions))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":85,"value":"countDistinctPositions(processTailMotions(motions))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":39,"value":"function* visualizeMotion(motions) {\n const positions = Array.from(processMotions(motions));\n const tailPositions = Array.from(processTailMotions(motions));\n for (let i = 0; i < tailPositions.length; ++i) {\n yield Plot.plot({\n grid: true,\n height: 640,\n x: {domain: d3.extent(positions, ([x]) => x)},\n y: {domain: d3.extent(positions, ([, y]) => y)},\n marks: [\n Plot.line(tailPositions.slice(0, i + 1), {}),\n Plot.line([tailPositions[i], positions[i]], {stroke: \"red\"})\n ]\n });\n }\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":51,"value":"input = FileAttachment(\"input.txt\").text()","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":52,"value":"motions = parseMotions(input)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":61,"value":"visualizeMotion(motions)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":153,"value":"k = 10","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":128,"value":"function* processRopeMotions(motions) {\n const RX = new Float64Array(k);\n const RY = new Float64Array(k);\n yield Array.from({length: k}, (_, i) => [RX[i], RY[i]]);\n for ([RX[0], RY[0]] of processMotions(motions)) {\n for (let i = 1; i < k; ++i) {\n [RX[i], RY[i]] = moveTail(RX[i], RY[i], RX[i - 1], RY[i - 1]);\n }\n yield Array.from({length: k}, (_, i) => [RX[i], RY[i]]);\n }\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":159,"value":"visualizeRopeMotion(motions)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":162,"value":"{\n const set = new Set();\n for (const ropePosition of processRopeMotions(motions)) {\n set.add(ropePosition[k - 1].join());\n }\n return set;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":148,"value":"function* visualizeRopeMotion(motions) {\n const positions = Array.from(processMotions(motions));\n const ropePositions = Array.from(processRopeMotions(motions));\n const tailPositions = ropePositions.map((rope) => rope[k - 1]);\n for (let i = 0; i < positions.length; ++i) {\n yield Plot.plot({\n grid: true,\n height: 640,\n x: {domain: d3.extent(positions, ([x]) => x)},\n y: {domain: d3.extent(positions, ([, y]) => y)},\n marks: [\n Plot.line(tailPositions.slice(0, i)),\n Plot.line(ropePositions[i], {stroke: \"red\"})\n ]\n });\n }\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W34","stdlib":"1","titling":"auto"}} 33:"$32:body"