Swift：如何在Swift中声明一个二维数组(网格或矩阵)以允许随机插入

struct Matrix2D<KeyElem:Hashable,Value> {

    var _storage:[KeyElem:[KeyElem:Value]] = [:]

    subscript(x:KeyElem,y:KeyElem) -> Value? {
        get {
            return _storage[x]?[y]
        }
        set(val) {
            if _storage[x] == nil {
                _storage[x] = [:]
            }
            _storage[x]![y] = val
        }
    }
}

var matrix = Matrix2D<Int,@R_772_10495@ng>()

matrix[1,2] = "foo"

as DictionaryLiteralConvertible：

extension Matrix2D:DictionaryLiteralConvertible {

    typealias Key = (x:KeyElem,y:KeyElem)

    init(DictionaryLiteral elements: (Key,value)...) {
        for (key,val) in elements {
            self[key.x,key.y] = val
        }
    }
}

var matrix:Matrix2D = [(1,2):"foo",(2,3):"bar"]

数组后端版本

struct Matrix2D<T> {

    var _storage:[[T?]] = []

    subscript(x:Int,y:int) -> T? {
       get {
            if _storage.count <= x {
                return nil
            }
            if _storage[x].count <= y {
                return nil
            }
            return _storage[x][y]
        }
        set(val) {
            if _storage.count <= x {
                let cols = [[T?]](count: x - _storage.count + 1,repeatedValue: [])
                _storage.extend(cols)
            }
            if _storage[x].count <= y {
                let rows = [T?](count: y - _storage[x].count + 1,repeatedValue: nil)
                _storage[x].extend(rows)
            }
            _storage[x][y] = val
        }
    }
}