HourglassScanner.swift

let input = [
    "1 1 1 0 0 0",
    "0 1 0 0 0 0",
    "1 1 1 0 0 0",
    "0 0 2 4 4 0",
    "0 0 0 2 0 0",
    "0 0 1 2 4 0"
]

let scanner = [
    "1 1 1",
    "0 1 0",
    "1 1 1"
]

struct Matrix {
    let value: [[Int8]]
    
    let rows: Int
    let cols: Int
    
    init(input: [String]) {
        value = input.map { value in value.characters.split(separator: " ").map { Int8(String($0))! } }
        
        rows = value[0].count
        cols = value.count
    }
    
    init(input: [[Int8]]) {
        value = input
        
        rows = input[0].count
        cols = input.count
    }
    
    func scan(_ input: Matrix, offset: (Int, Int)) -> Matrix {
        let inputArr = input.value
        let offsetX = Int(offset.0), offsetY = Int(offset.1)
        
        // scan here
        var scannedArr = [[Int8]]()
        for y in 0..<rows {
            let patternRow = value[y]
            let row = inputArr[offsetY+y]
            var scannedRow = [Int8]()
            for x in 0..<cols where patternRow[x] != 0 {
                let scannedValue = row[offsetX+x]
                scannedRow.append(scannedValue)
            }
            scannedArr.append(scannedRow)
        }
    
        return Matrix(input: scannedArr)
    }
}

func scan(matrix: Matrix, pattern: Matrix) -> [Matrix] {
    let w = matrix.rows-pattern.rows+1
    let h = matrix.cols-pattern.cols+1
    
    var examples = [Matrix]()
    for y in 0..<h {
        for x in 0..<w {
            examples.append(pattern.scan(matrix, offset: (x, y)))
        }
    }
    return examples
}

let scanned = scan(matrix: Matrix(input: input), pattern: Matrix(input: scanner))
let summed = scanned.map { value in
    return value.value.flatMap { $0 }.reduce(0, +)
}

summed.max()