Excel_Sheet_Column_Title.java

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