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
public class Solution { public String convertToTitle(int n) { if (n <= 0) return ""; StringBuilder sb = new StringBuilder(); while(n>0){ sb.insert(0,(char)('A' + (n-1)%26)); n = (n-1) / 26; } return sb.toString(); } }