一、前言

找工作這段鬧心的日子，繼續(xù)刷題吧...

二、Problem

Reverse Integer

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

Note:
The input is assumed to be a 32-bit signed integer. Your function should return 0 when the reversed integer overflows.

問(wèn)題的意思是給一個(gè)整數(shù)，進(jìn)行反轉(zhuǎn)后再返回。如果反轉(zhuǎn)后溢出了，則返回0。

三、Solution

思路是將輸入的整數(shù)轉(zhuǎn)化為字符串，遍歷該字符串的characters.reversed(),創(chuàng)建一個(gè)新字符串，如果遇到“-”號(hào)則插入到該字符串最前面，否則就插入到該字符串后面。最后使用可選綁定判斷是否溢出，進(jìn)行相應(yīng)的返回。

代碼如下：

class Solution {
    func reverse(_ x: Int) -> Int {
        let oldString = String(x)
        var newString = String()
        
        for character in oldString.characters.reversed() {
            if character == "-" {
                newString.insert(character, at: newString.startIndex)
            }else {
                newString.append(character)
            }
        }
        
        if let result = Int32(newString) {
            return Int(result)
        }else {
            return 0
        }
    }
}