chore(array) : readme file

Author: dhrubach

simple_array/README.md

@@ -0,0 +1,16 @@
+# problem list
+
+## easy
+
+- [Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/)
+- [K-Diff Pairs in an Array](https://leetcode.com/problems/k-diff-pairs-in-an-array/)
+- [Remove Duplicates from Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array/)
+
+## medium
+
+- [kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/)
+- [Remove Duplicates from Sorted Array II](https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/)
+
+## hard
+
+- [Best Time to Buy and Sell Stock III](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iii/)