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`35:[] 32:{"id":"4f423a0573f8cd4c","slug":"aoc-2019-day-3-crossed-wires","title":"AoC 2019, Day 3: Crossed Wires","thumbnail":"db6badf3891152c870ac56e557583a39b6c2943851f42c107b77b75336215206","access_level":"public","create_time":"$D2019-12-04T18:24:12.573Z","update_time":"$D2019-12-04T18:26:44.123Z","view_time":null,"first_public_time":"$D2019-12-04T18:26:58.537Z","has_unpublished_edits":null,"fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"df5b8f89744ab529","login":"jrunning","name":"Jordan Running","avatar_url":"https://avatars-next.observableusercontent.com/e72d7abc8db9954d704f85afa6bc2c66581a5ec0d30ebd00f56ae23d933944bd","tier":"starter_2024"},"version":44,"publish_version":44,"role":null,"authored":false,"authors":[{"type":"individual","id":"6130700aeb5dae38","login":"jrunning","name":"Jordan Running","avatar_url":"https://avatars-next.observableusercontent.com/e72d7abc8db9954d704f85afa6bc2c66581a5ec0d30ebd00f56ae23d933944bd","tier":null}],"members":[{"type":"individual","id":"6130700aeb5dae38","login":"jrunning","name":"Jordan Running","avatar_url":"https://avatars-next.observableusercontent.com/e72d7abc8db9954d704f85afa6bc2c66581a5ec0d30ebd00f56ae23d933944bd","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":{"id":"469040e4a7233bf4","slug":"advent-of-code-2019","title":"Advent of Code 2019","owner":{"id":"df5b8f89744ab529","login":"jrunning","name":"Jordan Running"}},"type":"notebook","body":{"title":"AoC 2019, Day 3: Crossed Wires","cells":[{"id":0,"value":"md`# AoC 2019, Day 3: Crossed Wires`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":5,"value":"md`## Input`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":8,"value":"$34","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":11,"value":"md`## Part 1`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":14,"value":"MATCH_WIRE_TURN = /([URDL])(\\d+)/g","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":17,"value":"/**\n * Takes a wire path as a string and returns an array of [dx,dy] vectors\n * @function parseWire\n * @param {string} wireStr\n * @return {Array>}\n * @example\n *\n * parseWire('R8,U5,L5,D3')\n * // => [[8, 0], [0, 5], [-5, 0], [0, -3]]\n */\nfunction parseWire(wireStr) {\n return [...wireStr.matchAll(MATCH_WIRE_TURN)].map(([, d, n]) => {\n n = parseInt(n);\n switch (d) {\n case 'U':\n return [0, n];\n case 'R':\n return [n, 0];\n case 'D':\n return [0, -n];\n case 'L':\n return [-n, 0];\n default:\n throw new Error(`Invalid turn '${d}${n}`);\n }\n });\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":20,"value":"/**\n * Takes one or more wire paths as strings and returns an array of arrays of [dx,dy] vectors\n * @param {string} wiresStr\n * @return {Array>}\n * @example\n *\n * parseWires(`R8,U5,L5,D3\\nU7,R6,D4,L4')\n * // => [\n * // [[8, 0], [0, 5], [-5, 0], [0, -3]]\n * // [[0, 7], [6, 0], [-4, 0], [0, -4]],\n * // ]\n */\nfunction parseWires(wiresStr) {\n return wiresStr.split('\\n').map(parseWire);\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":23,"value":"/**\n * Takes an array of [dx, dy] vectors and returns an array of [x, y] positions\n * @param {Array>} path\n * @return {Array>}\n */\nfunction wirePositions(path) {\n let x = 0;\n let y = 0;\n const positions = [];\n\n for (let [dx, dy] of path) {\n while (dx || dy) {\n let nextPos;\n if (dx > 0) {\n positions.push([(x += 1), y]);\n dx -= 1;\n } else if (dx < 0) {\n positions.push([(x -= 1), y]);\n dx += 1;\n } else if (dy > 0) {\n positions.push([x, (y += 1)]);\n dy -= 1;\n } else if (dy < 0) {\n positions.push([x, (y -= 1)]);\n dy += 1;\n }\n }\n }\n return positions;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":25,"value":"/** Builds a set of the points pathA crosses (as a sparse 2D array) */\npointsForWirePath = path =>\n wirePositions(path).reduce((positions, [x, y]) => {\n if (!positions[x]) {\n positions[x] = [];\n }\n positions[x][y] = true;\n return positions;\n }, [])","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":27,"value":"/**\n * Returns the Manhattan distance from the origin to nearest point where the given paths cross\n * @param {Array>} pathA\n * @param {Array>} pathB\n * @return {number}\n */\nfunction findSmallestCrossingDistance(pathA, pathB) {\n const positionsA = pointsForWirePath(pathA);\n\n // Iterate over the points pathB crosses and see if any of them belong to positionsA;\n // return the smallest\n return wirePositions(pathB).reduce((min, [x, y]) => {\n const dist = Math.abs(x) + Math.abs(y);\n return dist < min && positionsA[x] && positionsA[x][y] ? dist : min;\n }, Infinity);\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":29,"value":"{\n let answer;\n if (input.trim()) {\n const [pathA, pathB] = parseWires(input);\n answer = html`${findSmallestCrossingDistance(pathA, pathB)}`;\n } else {\n answer = html`no input`;\n }\n\n return md`**Answer:** ${answer}`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":33,"value":"md`## Part 2`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":36,"value":"/**\n * Takes an array of [dx, dy] vectors and returns an array of [x, y, d] positions where `d` is the\n * signal delay (number of steps in path)\n * @param {Array>} path\n * @return {Array>}\n */\nfunction wirePositionsWithSignalDelay(path) {\n let x = 0;\n let y = 0;\n let d = 1;\n const positions = [];\n\n for (let [dx, dy] of path) {\n while (dx || dy) {\n let nextPos;\n if (dx > 0) {\n positions.push([(x += 1), y, d++]);\n dx -= 1;\n } else if (dx < 0) {\n positions.push([(x -= 1), y, d++]);\n dx += 1;\n } else if (dy > 0) {\n positions.push([x, (y += 1), d++]);\n dy -= 1;\n } else if (dy < 0) {\n positions.push([x, (y -= 1), d++]);\n dy += 1;\n }\n }\n }\n return positions;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":38,"value":"/** Builds a sparse 2D array of the signal delay for each point given path crosses */\npointsForWirePathWithSignalDelay = path =>\n wirePositionsWithSignalDelay(path).reduce((positions, [x, y, d]) => {\n if (!positions[x]) {\n positions[x] = [];\n }\n positions[x][y] = d;\n return positions;\n }, [])","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":40,"value":"/**\n * Returns the Manhattan distance from the origin to nearest point where the given paths cross\n * @param {Array>} pathA\n * @param {Array>} pathB\n * @return {number}\n */\nfunction findSmallestCrossingSignalDelay(pathA, pathB) {\n // Build a set of the points pathA crosses (as a sparse 2D array)\n const positionsA = pointsForWirePathWithSignalDelay(pathA);\n\n // Iterate over the points pathB crosses and see if any of them belong to positionsA;\n // return the smallest\n return wirePositionsWithSignalDelay(pathB).reduce((dMin, [x, y, dB]) => {\n if (positionsA[x] && positionsA[x][y] !== undefined) {\n dMin = Math.min(dMin, positionsA[x][y] + dB);\n }\n return dMin;\n }, Infinity);\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":42,"value":"{\n let answer;\n if (input.trim()) {\n const [pathA, pathB] = parseWires(input);\n answer = html`${findSmallestCrossingSignalDelay(\n pathA,\n pathB\n )}`;\n } else {\n answer = html`no input`;\n }\n\n return md`**Answer:** ${answer}`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W35","stdlib":"1","titling":"auto"}} 33:"$32:body"