Create Solution.java

Author: Jerring

solution/0230.Kth Smallest Element in a BST/Solution.java

@@ -0,0 +1,17 @@
+class Solution {
+    public int kthSmallest(TreeNode root, int k) {
+        Deque<TreeNode> stack = new ArrayDeque<>();
+        while (!stack.isEmpty() || root != null) {
+            while (root != null) {
+                stack.push(root);
+                root = root.left;
+            }
+            root = stack.pop();
+            if (--k == 0) {
+                return root.val;
+            }
+            root = root.right;
+        }
+        return 0;
+    }
+}