230. Kth Smallest Element in a BST

C++/kth-smallest-element-in-a-bst.cpp

@@ -0,0 +1,35 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int kthSmallest(TreeNode* root, int k) {
+        int count = 0;
+        return inorder(root, k, count);
+    }
+
+private:
+    int inorder(TreeNode* node, int k, int& count) {
+        //Base case: Zero node
+        if(!node) return -1;
+
+        //Traverse left branch for kth smallest value:
+        int leftVal = inorder(node->left, k, count);
+        if(count == k) return leftVal;
+
+        //Process root node:
+        ++count;
+        if(count == k) return node->val; 
+
+        //Traverse right branch for kth smallest value:
+        return inorder(node->right, k, count);
+    }
+};

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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