Find the kth Smallest Element in a BST - Algorithm and Code Examples

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class Solution:
    def kthSmallest(self, root: TreeNode, k: int) -> int:
        self.count = 0
        self.ans = None
        def inorder(node):
            if not node or self.ans is not None:
                return
            inorder(node.left)
            self.count += 1
            if self.count == k:
                self.ans = node.val
                return
            inorder(node.right)
        inorder(root)
        return self.ans

# Example usage:
if __name__ == '__main__':
    # Construct BST:
    #       3
    #      / \
    #     1   4
    #      \
    #       2
    root = TreeNode(3, TreeNode(1, None, TreeNode(2)), TreeNode(4))
    sol = Solution()
    print(sol.kthSmallest(root, 1))