populating the BaseSeven.dart file

Author: Farial-mahmod

BaseSeven.dart

@@ -0,0 +1,12 @@
+// Leetcode Problem No. 504 : Given an integer num, return a string of its base 7 representation.
+// Leetcode Problem Link: https://leetcode.com/problems/base-7/
+// Result using Dart language here: Runtime: 485 ms, Memory Usage: 140.5 MB
+
+// Solution:
+
+// toRadixString is part of dart:core library
+class Solution {
+  String convertToBase7(int num) {
+      return num.toRadixString(7);
+  }
+}