ReverseInteger.swift

//
//  ReverseInteger.swift
//  LeetCode
//
//  Created by 黎赵太郎 on 25/11/2017.
//  Copyright © 2017 lizhaotailang. All rights reserved.
//
//  Given a 32-bit signed integer, reverse digits of an integer.
//
//  Example 1: Input: 123, Output:  321
//  Example 2: Input: -123, Output: -321
//
//  Have you thought about this?
//  Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!
//  If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100.
//  Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer, then the reverse of 1000000003 overflows.
//  How should you handle such cases?
//  For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
//
//  Note:
//  Assume we are dealing with an environment which could only hold integers within the 32-bit signed integer range.
//  For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
//
//  Accepted. See [ReverseIntegerTests](./LeetCode/ReverseIntegerTests.swift) for test cases.
//

import Foundation

class ReverseInteger {
    
    func reverse(_ x: Int) -> Int {
        if x == 0 {
            return 0
        }
        
        var result = 0
        var anotherX = x
        
        while anotherX != 0 {
            result = result * 10 + anotherX % 10
            anotherX /= 10
        }
        
        let intMax = 2147483647
        let intMin = -2147483648
        if (result > 0 && (result - intMax) > 0) || (result < 0 && (result - intMin) < 0) {
            return 0
        }
        
        return Int(result)
    }
    
}