Add solution 168.

Author: javadev

src/Algorithms/0168.excel-sheet-column-title/excel-sheet-column-title.php

@@ -0,0 +1,16 @@
+class Solution {
+
+    /**
+     * @param Integer $n
+     * @return String
+     */
+    function convertToTitle($n) {
+        $mapping = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];
+        $sb = "";
+        while($n > 0) {
+            $sb .= $mapping [--$n % 26]; //Since for a base 26 the numbers would be from 0 to 25. Deducting 1
+            $n = intval($n / 26);
+        }
+        return strrev($sb);
+    }
+}