30:[{"id":"6e660dc5663a2d07b476fc42e7b24b8114ae52808a8774ba9623a72efc611c43d601ab94224d1a33a4c392ebaad84079ae8ec985871370bae7932755ef377345","href":"https://static.observableusercontent.com/files/6e660dc5663a2d07b476fc42e7b24b8114ae52808a8774ba9623a72efc611c43d601ab94224d1a33a4c392ebaad84079ae8ec985871370bae7932755ef377345","name":"09_input.txt","type":"text/plain","lastModified":1639070849152.138,"size":10100}] 2e:{"title":"Day 9: Smoke Basin","cells":[{"id":0,"value":"# Day 9: Smoke Basin","pinned":false,"hidden":false,"mode":"md"},{"id":3,"value":"## Part 1","pinned":false,"hidden":false,"mode":"md"},{"id":26,"value":"getRiskLevel(input, lowPoints)","pinned":true,"hidden":false,"mode":"ojs"},{"id":39,"value":"lowPoints = getLowPoints(input)","pinned":true,"hidden":false,"mode":"ojs"},{"id":36,"value":"function getRiskLevel(scan, lowPoints) {\n return lowPoints.reduce((accumulator, currentValue, index, array) => {\n return accumulator + scan[currentValue[0]][currentValue[1]] + 1\n }, 0)\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":23,"value":"function getLowPoints(scan) {\n let lowPoints = []\n for (let row = 0; row < scan.length; row++) {\n for (let col = 0; col < scan[row].length; ++col) {\n let isLowPoint = true\n // check left\n if (col > 0)\n isLowPoint = isLowPoint && (scan[row][col] < scan[row][col - 1])\n // check up\n if (row > 0)\n isLowPoint = isLowPoint && (scan[row][col] < scan[row - 1][col])\n // check right\n if (col < scan[row].length - 1)\n isLowPoint = isLowPoint && (scan[row][col] < scan[row][col + 1])\n // check down\n if (row < scan.length - 1)\n isLowPoint = isLowPoint && (scan[row][col] < scan[row + 1][col])\n\n if (isLowPoint)\n lowPoints.push([row, col])\n }\n }\n\n return lowPoints\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":7,"value":"## Part 2","pinned":false,"hidden":false,"mode":"md"},{"id":61,"value":"basinSizes[0] * basinSizes[1] * basinSizes[2]","pinned":true,"hidden":false,"mode":"ojs"},{"id":46,"value":"basinSizes = getBasinSizes(input, lowPoints).sort( (a,b) => b-a )","pinned":true,"hidden":false,"mode":"ojs"},{"id":44,"value":"function getBasinSizes(scan, lowPoints) {\n // replace everything but 9s with 1s\n let tmpScan = Array()\n for (const row of scan) {\n tmpScan.push(row.map( height => height === 9 ? 9 : 1))\n }\n\n // Use flood fill to get the size of each basin\n let sizes = []\n for (const low of lowPoints) {\n // if the low point is in a previously filled basin, skip it\n if (tmpScan[low[0]][low[1]] === 0)\n continue\n\n let basinSize = 1\n tmpScan[low[0]][low[1]] = 0\n let neighborsToCheck = getNeighbors(tmpScan, low)\n while (neighborsToCheck.length > 0) {\n let neighbor = neighborsToCheck[0]\n if (tmpScan[neighbor[0]][neighbor[1]] === 1) {\n // increment the count and check the neighbors\n tmpScan[neighbor[0]][neighbor[1]] = 0\n neighborsToCheck.push(...getNeighbors(tmpScan, neighbor))\n basinSize++\n }\n neighborsToCheck.shift()\n }\n\n sizes.push(basinSize)\n }\n\n return sizes\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":51,"value":"function getNeighbors(scan, point) {\n let rowLength = scan[0].length\n let columnLength = scan.length\n let neighbors = []\n // check left\n if (point[0] > 0)\n neighbors.push([point[0] - 1, point[1]])\n // check up\n if (point[1] > 0)\n neighbors.push([point[0], point[1] - 1])\n // check right\n if (point[0] < rowLength - 1)\n neighbors.push([point[0] + 1, point[1]])\n // check down\n if (point[1] < columnLength - 1)\n neighbors.push([point[0], point[1] + 1])\n return neighbors\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":10,"value":"# Input","pinned":false,"hidden":false,"mode":"md"},{"id":19,"value":"testData = testInput.trim().split(\"\\n\").map( row => row.split(\"\").map(parseFloat))","pinned":true,"hidden":false,"mode":"ojs"},{"id":13,"value":"testInput = `\n2199943210\n3987894921\n9856789892\n8767896789\n9899965678`","pinned":true,"hidden":false,"mode":"ojs"},{"id":31,"value":"input = FileAttachment(\"09_input.txt\").text().then( txt => txt.trim().split(\"\\n\").map( row => row.split(\"\").map(parseFloat)))","pinned":true,"hidden":false,"mode":"ojs"}],"files":"$W30","stdlib":"1","titling":"auto"}