141 lines
3.7 KiB
Swift
141 lines
3.7 KiB
Swift
//
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// File.swift
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//
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//
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// Created by Max Nuding on 05.12.21.
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//
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import Foundation
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import Runner
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import Collections
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struct Coord: Hashable {
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let row: Int
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let col: Int
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func getLeft() -> Coord? {
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guard col > 0 else {
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return nil
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}
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return Coord(row: row, col: col - 1)
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}
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func getRight() -> Coord { Coord(row: row, col: col + 1) }
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func getAbove() -> Coord? {
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guard row > 0 else {
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return nil
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}
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return Coord(row: row - 1, col: col)
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}
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func getBelow() -> Coord { Coord(row: row + 1, col: col) }
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}
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struct Field:Sequence, IteratorProtocol {
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typealias Element = Coord
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let numbers: [[Int]]
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let numCols: Int
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let numRows: Int
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var neighbors = [Coord:[Coord]]()
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var current: Coord? = Coord(row: 0, col: 0)
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init(numbers: [[Int]]) {
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self.numbers = numbers
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numCols = numbers.first?.count ?? 0
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numRows = numbers.count
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}
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mutating func getNeighborsCoordsFor(coord: Coord) -> [Coord] {
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let n = neighbors[coord] ?? [coord.getAbove(), coord.getRight(), coord.getBelow(), coord.getLeft()]
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.compactMap { $0 }
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.filter { $0.row < numRows && $0.col < numCols }
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neighbors[coord] = n
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return n
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}
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mutating func isLowPointAt(coord: Coord) -> Bool {
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let value = self[coord]
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return getNeighborsCoordsFor(coord: coord)
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.map { numbers[$0.row][$0.col] }
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.allSatisfy { $0 > value }
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}
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private func getNextCoord() -> Coord? {
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guard let current = current else {
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return nil
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}
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if current.col == numCols - 1 && current.row == numRows - 1 {
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return nil
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}
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if current.col == numCols - 1 {
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return Coord(row: current.row + 1, col: 0)
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}
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return Coord(row: current.row, col: current.col + 1)
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}
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mutating func next() -> Coord? {
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defer {
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current = getNextCoord()
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}
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return current
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}
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subscript(index: Coord) -> Int {
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get {
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numbers[index.row][index.col]
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}/*
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set(newValue) {
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// Perform a suitable setting action here.
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}*/
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}
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}
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class Day09: Runnable {
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let inputPath: String
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var lowestNeighbors = [Coord: Coord]()
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var lowPoints = Set<Coord>()
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var field = Field(numbers: [[Int]]())
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required init(inputPath: String) {
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self.inputPath = inputPath
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}
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public func run() {
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let input = try! String(contentsOfFile: inputPath)
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let entries = input
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.trimmingCharacters(in: .newlines)
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.components(separatedBy: .newlines)
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.map { line in line.map { $0.wholeNumberValue! } }
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field = Field(numbers: entries)
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lowPoints = Set(field.filter { field.isLowPointAt(coord: $0) })
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//Part 1
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let sum = lowPoints.map { field[$0] }.reduce(0, +) + lowPoints.count
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print(sum)
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// Part 2:
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var basinSize = [Coord: Int]()
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for coord in field {
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guard field[coord] != 9 else {
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continue
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}
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let bl = basinLocation(for: coord)
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basinSize[bl, default: 0] += 1
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}
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let result = basinSize.values.sorted(by: >)[0..<3].reduce(1, *)
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print(result)
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}
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private func basinLocation(for coord: Coord) -> Coord {
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guard !lowPoints.contains(coord) else {
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return coord
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}
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let closestNeighbor = lowestNeighbors[coord] ?? field.getNeighborsCoordsFor(coord: coord).min(by: { field[$0] < field[$1] })!
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lowestNeighbors[coord] = closestNeighbor
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return basinLocation(for: closestNeighbor)
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}
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}
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