#221 is completed

Author: Hamid Gasmi

09-problems/lc_669_tree_bst.py

@@ -0,0 +1,67 @@
+class Tree_Node:
+     def __init__(self, val=0, left=None, right=None):
+         self.val = val
+         self.left = left
+         self.right = right
+
+class Solution:
+    
+    # Time Complexity: O(N)
+    # Space Complexity: O(1)
+    def trimBST(self, root: TreeNode, L: int, R: int) -> TreeNode:
+        
+        # 1. Find a common parent
+        node = root
+        while node is not None:
+            if node.val > R:
+                node = node.left
+                
+            elif node.val < L:
+                node = node.right
+            
+            else:
+                break
+        root = node
+        
+        # 2. Trim the left subtree
+        parent = root
+        node = root.left
+        while (node is not None):      
+            if node.val < L:
+                parent.left = node.right
+                node = node.right
+                
+            else:
+                parent = node
+                node = node.left
+        parent.left = None
+        
+        # 3. Trim the right subtree:
+        parent = root
+        node = root.right
+        while (node is not None):
+            if node.val > R:
+                parent.right = node.left
+                node = node.left
+            
+            else:
+                parent = node
+                node = node.right
+        parent.right = None
+        
+        return root
+    
+    def trimBST_recursive(self, root: TreeNode, L: int, R: int) -> TreeNode:
+        if not root:
+            return None
+        
+        elif root.val > R:
+            return self.trimBST(root.left, L, R)
+        
+        elif root.val < L:
+            return self.trimBST(root.right, L, R)
+        
+        root.left = self.trimBST(root.left, L, R)
+        root.right = self.trimBST(root.right, L, R)
+            
+        return root