Day 18; Queues and Stacks.swift

import Foundation

class Solution {
    var pushedCharacters: [Character] = []
    var enqueuedCharacters: [Character] = []
    var popHead = 0
    var enqueueHead = 0
  
    func pushCharacter(ch: Character) {
        self.pushedCharacters.append(ch)
    }
    
    func enqueueCharacter(ch: Character) {
        self.enqueuedCharacters.append(ch)
    }
    
    func popCharacter() -> Character {
        defer { popHead += 1 }
        return self.pushedCharacters[pushedCharacters.endIndex - popHead - 1]
    }
    
    func dequeueCharacter() -> Character {
        defer { enqueueHead += 1 }
        return self.enqueuedCharacters[enqueueHead]
    }
}

// read the string s.
let s = readLine()!

// create the Solution class object p.
let obj = Solution()

// push/enqueue all the characters of string s to stack.
for character in s {
    obj.pushCharacter(ch: character)
    obj.enqueueCharacter(ch: character)
}


var isPalindrome = true

// pop the top character from stack.
// dequeue the first character from queue.
// compare both the characters.
for _ in 0..<(s.count / 2) {
    if obj.popCharacter() != obj.dequeueCharacter() {
        isPalindrome = false

        break
    }
}

// finally print whether string s is palindrome or not.
if isPalindrome {
    print("The word, \(s), is a palindrome.")
} else {
    print("The word, \(s), is not a palindrome.")
}