Ben Ashton
1 year ago
2 changed files with 2313 additions and 0 deletions
@ -0,0 +1,121 @@
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import { readFileSync } from 'node:fs'; |
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const input = readFileSync('input', 'utf-8'); |
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const cubes = input |
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.split('\n') |
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.filter(line => !!line.trim()) |
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.map(coords => { |
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const [x, y, z] = coords.split(',').map(n => parseInt(n)); |
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return {x, y, z}; |
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}); |
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const surfaceArea = cubes.map(cubeA => { |
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const touchingCubes = cubes.filter(cubeB => { |
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const xDiff = Math.abs(cubeA.x - cubeB.x); |
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const yDiff = Math.abs(cubeA.y - cubeB.y); |
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const zDiff = Math.abs(cubeA.z - cubeB.z); |
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return ( |
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(xDiff === 1 && yDiff === 0 && zDiff === 0) || |
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(yDiff === 1 && zDiff === 0 && xDiff === 0) || |
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(zDiff === 1 && xDiff === 0 && yDiff === 0) |
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); |
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}); |
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const nonConnectedSides = 6 - touchingCubes.length; |
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return nonConnectedSides; |
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}).reduce((total, sides) => total + sides); |
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console.log(`The surface area of the droplet is: ${surfaceArea}`); |
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function minMax(dimension) { |
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return [ |
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cubes.reduce((min, coords) => Math.min(min, coords[dimension]), Infinity), |
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cubes.reduce((max, coords) => Math.max(max, coords[dimension]), -Infinity), |
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]; |
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} |
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function isCoordEqual(coordA, coordB) { |
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return coordA.every((v, i) => coordB[i] === v); |
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} |
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function uniqueCoordsFilter(coordA, i, coords) { |
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return coords.findLastIndex(coordB => isCoordEqual(coordA, coordB)) === i; |
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} |
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function getAllConnected(startX, startY, startZ, isConnected) { |
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const connected = []; |
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let toVisit = [[startX, startY, startZ]]; |
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while (true) { |
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connected.push(...toVisit); |
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toVisit = toVisit.flatMap(([x, y, z]) => [ |
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[x + 1, y, z ], |
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[x - 1, y, z ], |
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[x, y + 1, z ], |
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[x, y - 1, z ], |
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[x, y, z + 1], |
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[x, y, z - 1] |
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]) |
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.filter(coordA => |
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!connected.find(coordB => isCoordEqual(coordA, coordB)) |
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) |
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.filter(uniqueCoordsFilter) |
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.filter(([x, y, z]) => isConnected(x, y, z)); |
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if (!toVisit.length) { |
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break; |
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} |
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} |
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return connected; |
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} |
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const [minX, maxX] = minMax('x'); |
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const [minY, maxY] = minMax('y'); |
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const [minZ, maxZ] = minMax('z'); |
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// Get all coordinates external to droplet with a border of 2
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const connected = getAllConnected(minX - 2, minY - 2, minZ - 2, (x, y, z) => { |
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return ( |
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x >= minX - 2 && |
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x <= maxX + 2 && |
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y >= minY - 2 && |
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y <= maxY + 2 && |
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z >= minZ - 2 && |
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z <= maxZ + 2 && |
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// Not part of the droplet
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!cubes.find(coord => coord.x === x && coord.y === y && coord.z === z) |
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); |
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}); |
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// Calculate internal surface area of inverted droplet
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const externalSurfaceArea = connected.map(([ax, ay, az]) => { |
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// Skip coordinates right on the edge
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if ( |
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ax < minX - 1 || ax > maxX + 1 || |
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ay < minY - 1 || ay > maxY + 1 || |
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az < minZ - 1 || az > maxZ + 1 |
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) { |
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return 0; |
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} |
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const touchingCubes = connected.filter(([bx, by, bz]) => { |
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const xDiff = Math.abs(ax - bx); |
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const yDiff = Math.abs(ay - by); |
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const zDiff = Math.abs(az - bz); |
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return ( |
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(xDiff === 1 && yDiff === 0 && zDiff === 0) || |
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(yDiff === 1 && zDiff === 0 && xDiff === 0) || |
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(zDiff === 1 && xDiff === 0 && yDiff === 0) |
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); |
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}); |
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const nonConnectedSides = 6 - touchingCubes.length; |
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return nonConnectedSides; |
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}).reduce((total, sides) => total + sides); |
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console.log( |
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`The EXTERNAL surface area of the droplet is: ${externalSurfaceArea}` |
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); |
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