Adding readme file

Author: bugsweeper

168-ExcelSheetColumnTitle/README.md

@@ -0,0 +1,39 @@
+Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.
+
+For example:
+
+A -> 1
+B -> 2
+C -> 3
+...
+Z -> 26
+AA -> 27
+AB -> 28 
+...
+
+
+ 
+Example 1:
+
+Input: columnNumber = 1
+Output: "A"
+
+
+Example 2:
+
+Input: columnNumber = 28
+Output: "AB"
+
+
+Example 3:
+
+Input: columnNumber = 701
+Output: "ZY"
+
+
+ 
+Constraints:
+
+
+	1 <= columnNumber <= 231 - 1
+