2f:T451,// calc next positions of blizzards in the valley stepBlizzards = (valley) => { // start with a new valley map let nextValley = new Array(valley.length) .fill(0) .map((line) => new Array(valley[0].length).fill(0).map((el) => [])); // now loop in both directions and into values into each cell valley.forEach((line, y) => line.forEach((el, x) => el.forEach((val) => { // new position according to direction of blizzard (regard walls around) let newx = x; let newy = y; switch (val) { case "<": newx = x >= 2 ? x - 1 : valley[0].length - 2; break; case ">": newx = x <= valley[0].length - 3 ? x + 1 : 1; break; case "^": newy = y >= 2 ? y - 1 : valley.length - 2; break; case "v": newy = y <= valley.length - 3 ? y + 1 : 1; break; } // now add value to new coordinates in new map nextValley[newy][newx].push(val); }) ) ); // return the new valley map return nextValley; }30:Tc93,// iterative path finder function findPath = function* (valley, start, end) { // resulting list of found paths from start to end let validPaths = []; // take care of already visited cells to reduce size of posList let visited = new Map(); // list of positions under consideration let posList = [{ x: start.x, y: start.y, path: [] }]; // copy of (current) valley after 'step' steps let newValley = valley; // step counter (=0 for initial valley and start position) let step = -1; // list of valid positions (used for visualization only) let validPos = []; // as long as no path has been found yet ... while (validPaths.length == 0) { step++; validPos = []; let newPosList = []; // loop all positions under consideration posList.forEach((pos) => { if ( pos.x >= 0 && pos.y >= 0 && pos.x < valley[0].length && pos.y < valley.length ) { // this is a 'possible' position -> check if we've been here before (i.e. same step within the overall cycle of blizzards) let key = [step % cycleSize, pos.x, pos.y].join("-"); let steps = visited.get(key); if (!(steps <= step) && newValley[pos.y][pos.x].length == 0) { // position is valid (i.e. not known before and empty) validPos.push({ x: pos.x, y: pos.y, val: newValley[pos.y][pos.x] }); visited.set(key, step); // add position to path pos.path = pos.path .map((el) => Object.assign({}, el)) .concat([{ x: pos.x, y: pos.y }]); if (pos.x == end.x && pos.y == end.y) { // found finish line -> save a copy of the whole path validPaths.push(pos.path.map((coord) => Object.assign({}, coord))); } // now try out all 4 adjacent positions & a final wait state (stay in same position) newPosList.push({ x: pos.x - 1, y: pos.y, path: pos.path.map((el) => Object.assign({}, el)) }); newPosList.push({ x: pos.x + 1, y: pos.y, path: pos.path.map((el) => Object.assign({}, el)) }); newPosList.push({ x: pos.x, y: pos.y - 1, path: pos.path.map((el) => Object.assign({}, el)) }); newPosList.push({ x: pos.x, y: pos.y + 1, path: pos.path.map((el) => Object.assign({}, el)) }); newPosList.push({ x: pos.x, y: pos.y, path: pos.path.map((el) => Object.assign({}, el)) }); } } }); // intermediate output (for progress & for visualization) yield { step: step, posList: validPos, validPaths: validPaths, newValley: newValley }; // new positions are now under consideration in next loop posList = newPosList; // evaluate next state of blizzards (only if not already at final position) if (validPaths.length == 0) { newValley = stepBlizzards(newValley); } } // final output yield { step: step, posList: validPos, validPaths: validPaths, newValley: newValley }; }31:[{"id":"a70e7daee548b7f4ccc04a713ac69837d26d97eab37fa396b206b13148a7a4ac017df88b148e77043956a6c070549b835205aac65cda676c59250cbb59e0face","href":"https://static.observableusercontent.com/files/a70e7daee548b7f4ccc04a713ac69837d26d97eab37fa396b206b13148a7a4ac017df88b148e77043956a6c070549b835205aac65cda676c59250cbb59e0face","name":"input.txt","type":"text/plain","lastModified":1672648167904.019,"size":3321}] 2d:{"title":"Day 24 - Blizzard Basin","cells":[{"id":0,"value":"# Day 24 - Blizzard Basin","pinned":false,"hidden":false,"mode":"md"},{"id":22,"value":"inputs1 = `#.#####\n#.....#\n#>....#\n#.....#\n#...v.#\n#.....#\n#####.#`","pinned":true,"hidden":false,"mode":"ojs"},{"id":32,"value":"inputs0 = `#.######\n#>>.<^<#\n#.<..<<#\n#>v.><>#\n#<^v^^>#\n######.#`","pinned":true,"hidden":false,"mode":"ojs"},{"id":242,"value":"inputs = FileAttachment(\"input.txt\").text()","pinned":true,"hidden":false,"mode":"ojs"},{"id":35,"value":"// rearrange into 3d array (each map-cell might contain multiple values) and replace '.' by empty array [] value\nvalley = inputs\n .split(\"\\n\")\n .filter((line) => line.length > 0)\n .map((line) => line.split(\"\").map((el) => [el].filter((val) => val != \".\")))","pinned":true,"hidden":false,"mode":"ojs"},{"id":505,"value":"// find hole in array of wall values, i.e. [['#'],['#'],...]\nfindHole = function (line) {\n return line.reduce(\n (res, el, idx) => (res == null && el.length == 0 ? idx : res),\n null\n );\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":229,"value":"start = {\n return {\n x: findHole(valley[0]),\n y: 0\n };\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":236,"value":"end = {\n return {\n x: findHole(valley[valley.length - 1]),\n y: valley.length - 1\n };\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":187,"value":"cycleSize = (valley.length - 2) * (valley[0].length - 2)","pinned":true,"hidden":false,"mode":"ojs"},{"id":38,"value":"$2f","pinned":true,"hidden":false,"mode":"ojs"},{"id":427,"value":"// put found path into map for visualization\npath2Valley = function (path) {\n // start with a new empty map\n let valleyPath = new Array(path.newValley.length)\n .fill(0)\n .map((line) => new Array(path.newValley[0].length).fill(\".\"));\n\n // add walls\n path.newValley.forEach((line, y) =>\n line.forEach((el, x) => (valleyPath[y][x] = el.includes(\"#\") ? \"#\" : \".\"))\n );\n\n if (path.validPaths.length > 0) {\n // add found path with last digit of path index\n path.validPaths[0].forEach(\n (el, idx) => (valleyPath[el.y][el.x] = \"\" + (idx % 10))\n );\n } else {\n // add current positions under considerations as 'o'\n path.posList.forEach((el) => (valleyPath[el.y][el.x] = \"o\"));\n }\n\n // return the generated valley map\n return valleyPath;\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":177,"value":"// print a ASCII map with title\nprintValley = function (step, valley) {\n return html`\n

Step: ${step}

${valley\n      .map((line) => line.map((el) => el).join(\"\"))\n      .join(\"
\")}

\n `;\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":147,"value":"$30","pinned":true,"hidden":false,"mode":"ojs"},{"id":537,"value":"## Part 1 ","pinned":false,"hidden":false,"mode":"md"},{"id":343,"value":"pathToEnd = findPath(valley, start, end)","pinned":true,"hidden":false,"mode":"ojs"},{"id":195,"value":"printValley(pathToEnd.step, path2Valley(pathToEnd))","pinned":true,"hidden":false,"mode":"ojs"},{"id":201,"value":"result1 = pathToEnd.step","pinned":true,"hidden":false,"mode":"ojs"},{"id":539,"value":"## Part 2 ","pinned":false,"hidden":false,"mode":"md"},{"id":348,"value":"pathBackToStart = findPath(pathToEnd.newValley, end, start)","pinned":true,"hidden":false,"mode":"ojs"},{"id":434,"value":"printValley(pathBackToStart.step, path2Valley(pathBackToStart))","pinned":true,"hidden":false,"mode":"ojs"},{"id":352,"value":"pathToEndOnceAgain = findPath(pathBackToStart.newValley, start, end)","pinned":true,"hidden":false,"mode":"ojs"},{"id":472,"value":"printValley(pathToEndOnceAgain.step, path2Valley(pathToEndOnceAgain))","pinned":true,"hidden":false,"mode":"ojs"},{"id":356,"value":"result2 = pathToEnd.step + pathBackToStart.step + pathToEndOnceAgain.step","pinned":true,"hidden":false,"mode":"ojs"}],"files":"$W31","stdlib":"1","titling":"auto"}