Swift - find pattern that matches input pattern string

StringPatternMatch.playground

import UIKit

//Find matching pattern string as per input 'pattern' string


//****Input:
//var arStr = ["abbba"] //test 1
//var arStr = ["bbbaaa", "baaaa"]
//var arStr = ["bbbaaa", "baaaa", "abbbc", "abbba"]
var arStr = ["abbba", "bbbaaa", "cbbbc", "baaaa", "abbbc", "abbba"]
let pattern = "xyyyx" //pattern to match against

//-1) convert string pattern to array of strings
//let aP = Array(pattern.characters)
let pArr = pattern.characters.map { String($0) }
print("pArr: ", pArr)

//-2) Create keys for pattern to use -- using 0 and 1
//Note: using 'tuple' in switch statment
var newKeys = [Int]()
for (i, item) in pArr.enumerated() {
    switch (i,item) {
    case let (m,"x") where (m == 0 || m == 4):
        newKeys.append(0)
    case ( 1...3, "y"):
        newKeys.append(1)
    default:
        break
    }
}
print("newKeys: ", newKeys) //print out keys == mapped properly

//-3) map varialbe 'checkString' according to array of 'newKeys' values
var matchingArray = [String]()
for (i, item) in arStr.enumerated() {
    var checkString = ""
    for (k, indexValue) in newKeys.enumerated() {
        switch indexValue {
        case 0:
            //index of Character and character value
            let index = item.index(item.startIndex, offsetBy: indexValue)
            checkString.append(String(item[index]))
        case 1:
            let index = item.index(item.startIndex, offsetBy: indexValue)
            checkString.append(String(item[index]))
        default:
            break
        }
       // print("debug (check) -- tempString: ", tempString, "\n")
    }
    
    //if there is match we append it to 'matchingArray'
    if (checkString == item) {
        matchingArray.append(item)
    }
}

print("Matching Pattern - Array:", matchingArray)


//Tip:
//Another way to map string pattern to keys:
let pTest = "xyyyx"
let pTestArray = Array(pTest.characters)

var keysArray = [Int]()
//we map it to keys according position of the key as per their index
for (i, _) in pTestArray.enumerated() {
    switch i {
    case 0,4:
        keysArray.append(0)
    case 1...3:
        keysArray.append(1)
    default:
        break
    }
}
print("dbg-keysArray:", keysArray)

Xcode 9 - Swift 4

It should work with Xcode 8 and swift 3.