//: A UIKit based Playground for presenting user interface

import UIKit
import PlaygroundSupport
import Foundation

func reversedPolPost(_ input: String){
    var resultArray = [Character]()
    var sequencePriority = false
    var gap = 0 // gap for opertion prior
    var existOutOfSequencePriorityLowOperation = false
    var array = Array(input)
    for i in 0..<array.count {
        if array[i] == "+" || array[i] == "-" {
            if sequencePriority{
                resultArray.append(array[i])
                let temp = resultArray[resultArray.count-1]
                resultArray[resultArray.count-1] = resultArray[resultArray.count-2]
                resultArray[resultArray.count-2] = temp
            } else {
                resultArray.insert(array[i], at: 0)
                existOutOfSequencePriorityLowOperation = true
                gap += 1
            }
        }
        if array[i] == "*" || array[i] == "/" {
            if sequencePriority{
                resultArray.append(array[i])
                let temp = resultArray[resultArray.count-1]
                resultArray[resultArray.count-1] = resultArray[resultArray.count-2]
                resultArray[resultArray.count-2] = temp
            } else {
                existOutOfSequencePriorityLowOperation ? resultArray.insert(array[i], at: gap) : resultArray.insert(array[i], at: 0)
            }
        }
        if array[i] == "(" {
            sequencePriority = true
        }
        if array[i] == ")" {
            sequencePriority = false
        }
        if array[i].isNumber || array[i] == "."{ //number
            var gap = i
            while i < array.count { //(array[i].isNumber || array[i] == ".") &&
                if let _ = Int(String(array[gap])) {
                    resultArray.append(array[gap])
                    array[gap] = "n"
                    gap += 1
                } else {
                    if (array[gap] == "+" || array[gap] == "-" || array[gap] == "/" || array[gap] == "*") {
                        resultArray.insert(array[gap], at: gap-(gap-i))
                        array[gap] = "n"
                        break
                    }
                    if (array[gap] == ".") {
                        resultArray.append(array[gap])
                        array[gap] = "n"
                        gap += 1
                    }
                }
            }
            resultArray.append(" ")
        }
    }
    print(String(resultArray))
}

reversedPolPost("5+(874+1)*86+9")