20240618 Finished

src/problem/mod.rs

@@ -152,3 +152,4 @@ mod p222_count_complete_tree_nodes;
 mod p199_binary_tree_right_side_view;
 mod p637_average_of_levels_in_binary_tree;
 mod p530_minimum_absolute_difference_in_bst;
+mod p230_kth_smallest_element_in_a_bst;

src/problem/p230_kth_smallest_element_in_a_bst.rs

@@ -0,0 +1,72 @@
+/**
+ * [230] Kth Smallest Element in a BST
+ */
+pub struct Solution {}
+
+use crate::util::tree::{TreeNode, to_tree};
+
+// submission codes start here
+
+// Definition for a binary tree node.
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+//
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+use std::rc::Rc;
+use std::cell::RefCell;
+impl Solution {
+    fn inorder_iterate(node: &Rc<RefCell<TreeNode>>, count: &mut i32, target: i32) -> Option<i32> {
+        if let Some(left) = node.borrow().left.as_ref() {
+            if let Some(result) = Self::inorder_iterate(left, count, target) {
+                return Some(result);
+            }
+        };
+
+        *count += 1;
+        if *count == target {
+            return Some(node.borrow().val);
+        }
+
+        if let Some(right) = node.borrow().right.as_ref() {
+            if let Some(result) =  Self::inorder_iterate(right, count, target) {
+                return Some(result);
+            }
+        }
+
+        None
+    }
+
+    pub fn kth_smallest(root: Option<Rc<RefCell<TreeNode>>>, k: i32) -> i32 {
+        let mut count = 0;
+
+        if let Some(root) = root {
+            return Self::inorder_iterate(&root, &mut count, k).unwrap()
+        }
+
+        0
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_230() {
+    }
+}