https://leetcode.com/problems/excel-sheet-column-title/

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"

程式碼：

class Solution {
public:
    string convertToTitle(int n) {
        string ans;
        int cnt = 0;
        while(n) {
            if(n % 26 == 0) {
                ans[cnt ++] = 'Z';
                n -= 26;
            } else {
                ans[cnt ++] = 'A' - 1 + (n % 26);
                n -= n % 26;
            }
            n /= 26;
        }
        for(int i = 0; i < cnt / 2; i ++)
            swap(ans[i], ans[cnt - i - 1]);
        
        return ans;
    }
};

　　每次 $n$ 要減去 $n % 26$ 然後再 $n / 26$ 還有要注意的就是當 $n$ 可以被 $26$ 整除的時候要特別寫一下 唉 這個題看了半天