Convert an array to matrix to find adjacent elements iOS swift - ios

Question

Convert this below array into matrix
Array
let ptsArray = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
Matrix
0 1 2 3 4 5
6 7 8 9 10 11
12 13 14 15 16 17
To find adjacent points in uniderectional like an below image
Expected output
(0,1) (0,6)
(1,2) (1,7)
(2,3) (2,8)
(3,4) (3,9)
(4,5) (4,10)
(5,11)
(6,7) (6,12)
(7,8) (7,13)
(8,9) (8,14)
(9,10) (9,15)
(10,11) (10,16)
(11,17)
(12,13)
(13,14)
(14,15)
(15,16)
(16,17)
My failed approach
for i in 0..<pointsArray.count-1{
if (i+1)%6 == 0 && i != 0{
print("Connection (\(i),\(i+6))")
nodesArray[i].addConnection(to: nodesArray[i+6], bidirectional: true, weight: 1)
}
if i>=pointsArray.count-6{
print("Connection (\(i),\(i+1))")
nodesArray[i].addConnection(to: nodesArray[i+1], bidirectional: true, weight: 1)
}
else{
print("Connection (\(i),\(i+1)) (\(i),\(i+6))")
nodesArray[i].addConnection(to: nodesArray[i+1], bidirectional: true, weight: 1)
nodesArray[i].addConnection(to: nodesArray[i+6], bidirectional: true, weight: 1)
}
}
Output:
Connection (0,1) (0,6)
Connection (1,2) (1,7)
Connection (2,3) (2,8)
Connection (3,4) (3,9)
Connection (4,5) (4,10)
Connection (5,11)
Connection (5,6) (5,11)
Connection (6,7) (6,12)
Connection (7,8) (7,13)
Connection (8,9) (8,14)
Connection (9,10) (9,15)
Connection (10,11) (10,16)
Connection (11,17)
Connection (11,12) (11,17)
Connection (12,13)
Connection (13,14)
Connection (14,15)
Connection (15,16)
Connection (16,17)

Answer 1

In the desired output, I guess that it's missing (9,15), (10,11), (10,16) and that (10,15) isn't valid.
If we think about your desired output, we notice something.
Let's name width = 6, it's the "width" of your matrix.
We see the pattern:
(value, value + 1), (value, value + width)
With some excluded tests: does (value + width) exists ? And we are not at the end of the width.
Let's, with a little reduce method:
let ptsArray = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
let width = 6
let tuples = ptsArray.indices.reduce(into: [(Int, Int)]()) { partialResult, anIndex in
if ptsArray.count > anIndex.advanced(by: 1) && anIndex % width != width - 1 {
let newValue = (ptsArray[anIndex], ptsArray[anIndex.advanced(by: 1)])
print(newValue)
partialResult.append(newValue)
}
if ptsArray.count > anIndex.advanced(by: width) {
let newValue = (ptsArray[anIndex], ptsArray[anIndex.advanced(by: width)])
print(newValue)
partialResult.append(newValue)
}
return
}
print(tuples)
I used "index", because in fact, points are in order here, but it could be any value, no? So let's use the index instead.
So, with something a little more generic:
extension Array {
func coupling(with width: Int) -> [(Element, Element)] {
let couples = indices.reduce(into: [(Element, Element)]()) { partialResult, anIndex in
if count > anIndex.advanced(by: 1) && anIndex % width != width - 1 {
let newValue = (self[anIndex], self[anIndex.advanced(by: 1)])
partialResult.append(newValue)
}
if count > anIndex.advanced(by: width) {
let newValue = (self[anIndex], self[anIndex.advanced(by: width)])
partialResult.append(newValue)
}
return
}
return couples
}
}
Use:
let ptsArray = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
let tuples2 = ptsArray. coupling(with: width)
print(tuples2)
let lettersArray = ["A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P", "Q", "R"]
let tuples3 = lettersArray. coupling(with: width)
print(tuples3)

Answer 2

Another approach - convert your ptsArray into a 2-D matrix:
var matrix: [[Int]] = []
let numCols: Int = 6
var numRows: Int = 0
let ptsArray: [Int] = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
for i in stride(from: 0, to: ptsArray.count, by: numCols) {
// make sure we don't exceed the array limit
if ptsArray.count >= i+numCols {
matrix.append(Array(ptsArray[i..<i+numCols]))
}
}
numRows = matrix.count
You can now get the right and down values (if they exist) like this:
func getPair2D(_ n: Int) -> (Int?, Int?) {
let thisRow = n / numCols
let thisCol = n % numCols
let numToRight = thisCol < numCols-1 ? matrix[thisRow][thisCol+1] : nil
let numToDown = thisRow < numRows-1 ? matrix[thisRow+1][thisCol] : nil
return (numToRight, numToDown)
}
and this will print out the results:
for i in 0..<ptsArray.count {
let (n1, n2) = getPair2D(i)
var str = ""
if let n1 = n1 {
str += "(\(i), \(n1))"
}
if let n2 = n2 {
if !str.isEmpty { str += " " }
str += "(\(i), \(n2))"
}
print(str)
}
Here's a simple view controller that let's you tap any number to show the "right and down" matches:
class MatrixVC: UIViewController {
var matrix: [[Int]] = []
var views: [UIView] = []
let numCols: Int = 6
var numRows: Int = 0
override func viewDidLoad() {
super.viewDidLoad()
let ptsArray: [Int] = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
for i in stride(from: 0, to: ptsArray.count, by: numCols) {
if ptsArray.count >= i+numCols {
matrix.append(Array(ptsArray[i..<i+numCols]))
}
}
numRows = matrix.count
let oStack: UIStackView = {
let v = UIStackView()
v.axis = .vertical
v.distribution = .fillEqually
v.spacing = 2
return v
}()
var n = 0
for r in 0..<numRows {
let rStack: UIStackView = {
let v = UIStackView()
v.axis = .horizontal
v.distribution = .fillEqually
v.spacing = 2
return v
}()
for c in 0..<numCols {
let v = UILabel()
v.textAlignment = .center
v.text = "\(ptsArray[n])"
v.isUserInteractionEnabled = true
let t = UITapGestureRecognizer(target: self, action: #selector(gotTap(_:)))
v.addGestureRecognizer(t)
rStack.addArrangedSubview(v)
views.append(v)
if c < numCols-1 {
let iv = UIImageView(image: UIImage(systemName: "arrow.right"))
rStack.addArrangedSubview(iv)
}
n += 1
}
oStack.addArrangedSubview(rStack)
if r < numRows-1 {
let rStack: UIStackView = {
let v = UIStackView()
v.axis = .horizontal
v.distribution = .fillEqually
v.spacing = 2
return v
}()
for c in 0..<numCols {
let iv = UIImageView(image: UIImage(systemName: "arrow.down"))
rStack.addArrangedSubview(iv)
if c < numCols-1 {
let v = UIView()
rStack.addArrangedSubview(v)
}
}
oStack.addArrangedSubview(rStack)
}
}
oStack.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(oStack)
let g = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
oStack.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
oStack.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
oStack.centerXAnchor.constraint(equalTo: g.centerXAnchor),
oStack.centerYAnchor.constraint(equalTo: g.centerYAnchor),
])
}
#objc func gotTap(_ g: UITapGestureRecognizer) {
guard let v = g.view as? UILabel,
let t = v.text,
let n = Int(t)
else { return }
// if the tapped label is yellow, let's just deselect all
let deselecting: Bool = views[n].backgroundColor == .yellow
views.forEach { $0.backgroundColor = .clear }
if deselecting {
return()
}
views[n].backgroundColor = .yellow
let (n1, n2) = getPair2D(n)
if let n1 = n1 {
views[n1].backgroundColor = .yellow
}
if let n2 = n2 {
views[n2].backgroundColor = .yellow
}
}
func getPair2D(_ n: Int) -> (Int?, Int?) {
let thisRow = n / numCols
let thisCol = n % numCols
let numToRight = thisCol < numCols-1 ? matrix[thisRow][thisCol+1] : nil
let numToDown = thisRow < numRows-1 ? matrix[thisRow+1][thisCol] : nil
return (numToRight, numToDown)
}
}
It looks like this:
Tapping any number will highlight the pair:
Tapping a "highlighted" number will "un-highlight" all numbers.