# 168 Excel Sheet Column Title

給一個integer，求Excel Column的英文字母title。

Concept:

觀察一下

1 -> A

27 -> AA

28 -> AB

28 % 26 = 2 -> B

(27 - 2)/26 = 1

1 % 26 = 1 -> A

(1 - 1)/26 = 0 -> done.

Pseudocode:

use a stringbuilder sb to build column title
declare 2 int variable, division =  and carry
while if n > 0
  char c = 65+(n%26)-1
  sb.append(c)
  carry = n % 26
  n = n / 26
sb.append(carry)
return sb.reverse().toString
**notice: edge case-> 26

完整程式碼：

public class Solution {
    public String convertToTitle(int n) {
        StringBuilder sb = new StringBuilder();
        int carry;
        if(n==0) return "";
        while(n>0){
            carry = n % 26;
            if(carry==0)   carry = 26;
            char c = (char)(65+carry-1);
            sb.append(c);
            n = (n-carry)/26;
        }
        return sb.reverse().toString();
    }
}