[Swift]LeetCode168. Excel表列名称 | Excel Sheet Column Title

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Given a positive integer, return its corresponding column title as appear in an Excel sheet.

For example:

    1 -> A
    2 -> B
    3 -> C
    ...
    26 -> Z
    27 -> AA
    28 -> AB 
    ...

Example 1:

Input: 1
Output: "A"

Example 2:

Input: 28
Output: "AB"

Example 3:

Input: 701
Output: "ZY"

---

给定一个正整数，返回它在 Excel 表中相对应的列名称。

例如，

    1 -> A
    2 -> B
    3 -> C
    ...
    26 -> Z
    27 -> AA
    28 -> AB 
    ...

示例 1:

输入: 1
输出: "A"

示例 2:

输入: 28
输出: "AB"

示例 3:

输入: 701
输出: "ZY"

---

class Solution {
    func convertToTitle(_ n: Int) -> String {
        var m:Int = n
        var temp:String = String()
        while(m > 0)
        {
            //A的ASCII为65
            var num:Int = (m - 1) % 26 + 65
            var s:Character = Character(UnicodeScalar(num)!)
            temp = String(s) + temp
            m = (m - 1)/26
        }
        return temp
    }
}

---

8ms

class Solution {
    func convertToTitle(_ n: Int) -> String {
        
        guard n > 0 else {
            return ""
        }
        var result = [Character]()
        var n = n
        while n > 0 {
            n = n - 1
            let a = n % 26 
            result.append(Character(UnicodeScalar(Int(65) + a )!))
            n /= 26
        }
        
        return String(result.reversed())
        
    }
}

---

12ms

class Solution {
    func convertToTitle(_ n: Int) -> String {
        var result = ""
        var x = n
        while x > 0 {
            x -= 1
            result = String(Character(UnicodeScalar(x % 26 + 65)!)) + result
            x = x / 26
        }
        return result
    }
}