aoc2021/Sources/09/09.swift

98 lines
2.4 KiB
Swift

//
// File.swift
//
//
// Created by Max Nuding on 05.12.21.
//
import Foundation
import Runner
import Collections
struct Coord {
let row: Int
let col: Int
func getLeft() -> Coord? {
guard col > 0 else {
return nil
}
return Coord(row: row, col: col - 1)
}
func getRight() -> Coord { Coord(row: row, col: col + 1) }
func getAbove() -> Coord? {
guard row > 0 else {
return nil
}
return Coord(row: row - 1, col: col)
}
func getBelow() -> Coord { Coord(row: row + 1, col: col) }
}
struct Field:Sequence, IteratorProtocol {
let numbers: [[Int]]
let numCols: Int
let numRows: Int
var current: Coord? = Coord(row: 0, col: 0)
init(numbers: [[Int]]) {
self.numbers = numbers
numCols = numbers.first!.count
numRows = numbers.count
}
func getNeighborsCoordsFor(coord: Coord) -> [Coord] {
return [coord.getAbove(), coord.getRight(), coord.getBelow(), coord.getLeft()]
.compactMap { $0 }
.filter { $0.row < numRows && $0.col < numCols }
}
func lowPointValueAt(coord: Coord) -> Int? {
let value = numbers[coord.row][coord.col]
return getNeighborsCoordsFor(coord: coord)
.map { numbers[$0.row][$0.col] }
.allSatisfy { $0 > value }
? value
: nil
}
private func getNextCoord() -> Coord? {
guard let current = current else {
return nil
}
if current.col == numCols - 1 && current.row == numRows - 1 {
return nil
}
if current.col == numCols - 1 {
return Coord(row: current.row + 1, col: 0)
}
return Coord(row: current.row, col: current.col + 1)
}
mutating func next() -> Coord? {
defer {
current = getNextCoord()
}
return current
}
}
struct Day09: Runnable {
let inputPath: String
func run() {
let input = try! String(contentsOfFile: inputPath)
let entries = input
.trimmingCharacters(in: .newlines)
.components(separatedBy: .newlines)
.map { line in line.map { $0.wholeNumberValue! } }
let field = Field(numbers: entries)
let sum = field.compactMap { field.lowPointValueAt(coord: $0) }.reduce(0, { $0 + $1 + 1 })
print(sum)
}
}