Create 0450-delete-node-in-a-bst.kt

Author: a93a

kotlin/0450-delete-node-in-a-bst.kt

@@ -0,0 +1,36 @@
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+
+//recursive solution
+class Solution {
+    fun deleteNode(root: TreeNode?, key: Int): TreeNode? {
+        
+        root?: return null
+
+        if (root.value < key) {
+            root.right = deleteNode(root.right, key)
+        } else if (root.value > key) {
+            root.left = deleteNode(root.left, key)
+        } else {
+            if (root.right == null) return root.left
+            if (root.left == null) return root.right
+
+            var current = root.right
+            while (current.left != null) current = current.left
+            root.`val` = current.value
+            root.right = deleteNode(root.right, root.value)
+        }
+
+        return root
+    }
+
+    private val TreeNode.value get() = `val`
+}