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 

Credits:

Special thanks to @ifanchu for adding this problem and creating all test cases.

public class Solution {

    public String convertToTitle(int n) {

        char a[]=new char[27];

        a[0]='A';

        for(int i=1;i<=26;i++){

            a[i]=(char)(a[0]+i-1);

        }

        if(n<=26)

            return (a[n]+"");

        String s="";

        while(n>26){

            int r = n%26;

            if(r==0){

                r=26;

                n-=26;

            }

            s = a[r]+s;

            n/=26;

        }

        s = a[n]+s;

        return s;

    }

}