Discussion on: Advent of Code 2019 Solution Megathread - Day 8: Space Image Format

import Cocoa

let width = 25
let tall = 6

let digits = input.compactMap{ Int(String($0))}
let numberOfLayer = digits.count/(width * tall)

var startIndex = 0
let layers = (1...numberOfLayer).map{ layerNumber -> Array<Int> in
    let count = (width * tall) * layerNumber
    let layer = digits[startIndex..<count]
    startIndex = count
    return Array(layer)
}

func partTwo() {
    var result: [Int] = Array.init(repeating: 0, count: width * tall)

    let first = layers.first!

    for (index,value) in first.enumerated() {
        if value == 0 || value == 1 {
            result[index] = value
        }
        else {
            for layer in layers.dropFirst() {
                if (layer[index] == 0 || layer[index] == 1) {
                    result[index] = layer[index]
                    break
                }
            }
        }
    }

    startIndex = 0
    while true {
        let count = width + startIndex
        let value = result[startIndex..<count]
        startIndex = count
        print(value)
        if startIndex >= result.count {
            break
        }
    }
}

func partOne() {
    var low:[Int] = []
    var lowestCount: Int = Int.max
    for layer in layers {
        let dict = layer.reduce(into: [:]) { counts, number in
            counts[number, default: 0] += 1
        }
        let count = dict[0]
        if let count = count {
            if count < lowestCount {
                lowestCount = count
                low = layer
            }
        }
    }
    let dict = low.reduce(into: [:]) { counts, number in
        counts[number, default: 0] += 1
    }
    let result = (dict[1] ?? 0) * (dict[2] ?? 0)
    print("Result is : \(result)")
}

partOne()
partTwo()