added solution for 230. Kth Smallest Element in a BST + updated README + Table Entry under DFS

Author: n1i9c9k9

README.md

@@ -359,6 +359,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 | 110  | [Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/)                                | [Java](./Java/Balanced-Binary-Tree.java)           | _O(n)_      | _O(n)_      | Easy       | DFS |      |
 | 1376 | [ Time Needed to Inform All Employees](https://leetcode.com/problems/time-needed-to-inform-all-employees/) | [C++](./C++/Cherry-Pickup-II.cpp)                  | _O(n)_      | _O(n)_      | Medium     | DFS |      |
 | 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands/)                                       | [C++](./C++/number-of-islands.cpp)                  | _O(m * n)_ | _O(m * n)_ | Medium     | DFS |      |
+| 230 | [Kth Smallest Element in a BST](https://leetcode.com/problems/kth-smallest-element-in-a-bst/)                                       | [C++](./C++/kth-smallest-element-in-a-bst.cpp)                  | _O(n)_ | _O(n)_ | Medium     | DFS |      |
 
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@@ -515,6 +516,7 @@ DISCLAIMER: This above mentioned resources have affiliate links, which means if
 | [Shrimadh V Rao](https://github.com/Shrimadh) <br> <img src="https://avatars.githubusercontent.com/u/64469917?v=4" width="100" height="100">                                                                   | India          | C++                  |  [GitHub](https://github.com/Shrimadh)
 | [Shreyas Shrawage](https://github.com/shreyventure) <br> <img src = "https://avatars.githubusercontent.com/u/55741087?v=4" width="100" height="100"> | India | Python | [CodeChef](https://www.codechef.com/users/shreyventure)<br/>[LeetCode](https://leetcode.com/shreyventure/)<br/>[HackerRank](https://www.hackerrank.com/shreyas_shrawage)
 | [Surbhi Mayank](https://github.com/surbhi2408) <br> <img src="https://avatars.githubusercontent.com/u/58289829?s=400&u=68fd396819b927ec4d8820d87d6d1e311c3abd01&v=4" width="100" height="100">                                                                   | India          | C++                  |  [GitHub](https://github.com/surbhi2408)
+| [Nick H](https://github.com/n1i9c9k9) <br> <img src="https://github.com/n1i9c9k9.png" width="100" height="100">                                                                   | Germany          | C++                  |  [GitHub](https://github.com/n1i9c9k9)
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