AoC2022-Day18-Part2.swift

import UIKit

var input =
"""
2,2,2
1,2,2
3,2,2
2,1,2
2,3,2
2,2,1
2,2,3
2,2,4
2,2,6
1,2,5
3,2,5
2,1,5
2,3,5
"""

let lines = input.split(whereSeparator: \.isNewline)

struct Cube: Equatable, Hashable {
    let x: Int
    let y: Int
    let z: Int
    
    var coordTopEdge: Coordinate {
        Coordinate(p1: x, p2: z)
    }
    
    var coordLeftEdge: Coordinate {
        Coordinate(p1: y, p2: z)
    }
    
    var coordFrontEdge: Coordinate {
        Coordinate(p1: x, p2: y)
    }
}

struct Coordinate: Equatable, Hashable {
    let p1: Int
    let p2: Int
}

var cubes: Set<Cube> = []

var topEdges: [Coordinate: Int] = [:]
var bottomEdges: [Coordinate: Int] = [:]
var leftEdges: [Coordinate: Int] = [:]
var rightEdges: [Coordinate: Int] = [:]
var frontEdges: [Coordinate: Int] = [:]
var backEdges: [Coordinate: Int] = [:]

for line in lines {
    let coords = line.split(separator: ",")
    let cube = Cube(x: Int(String(coords[0]))!, y: Int(String(coords[1]))!, z: Int(String(coords[2]))!)
    cubes.insert(cube)
    
    if topEdges[cube.coordTopEdge] == nil {
        topEdges[cube.coordTopEdge] = cube.y
    } else {
        topEdges[cube.coordTopEdge] = max(cube.y, topEdges[cube.coordTopEdge]!)
    }
    
    if bottomEdges[cube.coordTopEdge] == nil {
        bottomEdges[cube.coordTopEdge] = cube.y
    } else {
        bottomEdges[cube.coordTopEdge] = min(cube.y, bottomEdges[cube.coordTopEdge]!)
    }
    
    if leftEdges[cube.coordLeftEdge] == nil {
        leftEdges[cube.coordLeftEdge] = cube.x
    } else {
        leftEdges[cube.coordLeftEdge] = min(cube.x, leftEdges[cube.coordLeftEdge]!)
    }
    
    if rightEdges[cube.coordLeftEdge] == nil {
        rightEdges[cube.coordLeftEdge] = cube.x
    } else {
        rightEdges[cube.coordLeftEdge] = max(cube.x, rightEdges[cube.coordLeftEdge]!)
    }
    
    if frontEdges[cube.coordFrontEdge] == nil {
        frontEdges[cube.coordFrontEdge] = cube.z
    } else {
        frontEdges[cube.coordFrontEdge] = min(cube.z, frontEdges[cube.coordFrontEdge]!)
    }
    
    if backEdges[cube.coordFrontEdge] == nil {
        backEdges[cube.coordFrontEdge] = cube.z
    } else {
        backEdges[cube.coordFrontEdge] = max(cube.z, backEdges[cube.coordFrontEdge]!)
    }
}

var surfaceArea = 0

for cube in cubes {
    let top = Cube(x: cube.x, y: cube.y + 1, z: cube.z)
    let bottom = Cube(x: cube.x, y: cube.y - 1, z: cube.z)
    let left = Cube(x: cube.x - 1, y: cube.y, z: cube.z)
    let right = Cube(x: cube.x + 1, y: cube.y, z: cube.z)
    let front = Cube(x: cube.x, y: cube.y, z: cube.z + 1)
    let back = Cube(x: cube.x, y: cube.y, z: cube.z - 1)
    
    let check: Set<Cube> = [top, bottom, left, right, front, back]
    let intersect = cubes.intersection(check)
    surfaceArea += (6 - intersect.count)
}

print(surfaceArea)

print(topEdges.count + bottomEdges.count + leftEdges.count + rightEdges.count + frontEdges.count + backEdges.count)