From e0017c4d9c9ec6a7d3903f01e96ca3d7005f56db Mon Sep 17 00:00:00 2001
From: Madhur Kabra <madhur.kabra@spit.ac.in>
Date: Tue, 29 Oct 2019 22:36:53 +0530
Subject: [PATCH] Create AVL tree insertion

---
 AVL tree insertion | 139 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 AVL tree insertion

diff --git a/AVL tree insertion b/AVL tree insertion
new file mode 100644
index 0000000..3ae45c0
--- /dev/null
+++ b/AVL tree insertion	
@@ -0,0 +1,139 @@
+class TreeNode(object): 
+    def __init__(self, val): 
+        self.val = val 
+        self.left = None
+        self.right = None
+        self.height = 1
+  
+# AVL tree class which supports the  
+# Insert operation 
+class AVL_Tree(object): 
+  
+    # Recursive function to insert key in  
+    # subtree rooted with node and returns 
+    # new root of subtree. 
+    def insert(self, root, key): 
+      
+        # Step 1 - Perform normal BST 
+        if not root: 
+            return TreeNode(key) 
+        elif key < root.val: 
+            root.left = self.insert(root.left, key) 
+        else: 
+            root.right = self.insert(root.right, key) 
+  
+        # Step 2 - Update the height of the  
+        # ancestor node 
+        root.height = 1 + max(self.getHeight(root.left), 
+                           self.getHeight(root.right)) 
+  
+        # Step 3 - Get the balance factor 
+        balance = self.getBalance(root) 
+  
+        # Step 4 - If the node is unbalanced,  
+        # then try out the 4 cases 
+        # Case 1 - Left Left 
+        if balance > 1 and key < root.left.val: 
+            return self.rightRotate(root) 
+  
+        # Case 2 - Right Right 
+        if balance < -1 and key > root.right.val: 
+            return self.leftRotate(root) 
+  
+        # Case 3 - Left Right 
+        if balance > 1 and key > root.left.val: 
+            root.left = self.leftRotate(root.left) 
+            return self.rightRotate(root) 
+  
+        # Case 4 - Right Left 
+        if balance < -1 and key < root.right.val: 
+            root.right = self.rightRotate(root.right) 
+            return self.leftRotate(root) 
+  
+        return root 
+  
+    def leftRotate(self, z): 
+  
+        y = z.right 
+        T2 = y.left 
+  
+        # Perform rotation 
+        y.left = z 
+        z.right = T2 
+  
+        # Update heights 
+        z.height = 1 + max(self.getHeight(z.left), 
+                         self.getHeight(z.right)) 
+        y.height = 1 + max(self.getHeight(y.left), 
+                         self.getHeight(y.right)) 
+  
+        # Return the new root 
+        return y 
+  
+    def rightRotate(self, z): 
+  
+        y = z.left 
+        T3 = y.right 
+  
+        # Perform rotation 
+        y.right = z 
+        z.left = T3 
+  
+        # Update heights 
+        z.height = 1 + max(self.getHeight(z.left), 
+                        self.getHeight(z.right)) 
+        y.height = 1 + max(self.getHeight(y.left), 
+                        self.getHeight(y.right)) 
+  
+        # Return the new root 
+        return y 
+  
+    def getHeight(self, root): 
+        if not root: 
+            return 0
+  
+        return root.height 
+  
+    def getBalance(self, root): 
+        if not root: 
+            return 0
+  
+        return self.getHeight(root.left) - self.getHeight(root.right) 
+  
+    def preOrder(self, root): 
+  
+        if not root: 
+            return
+  
+        print("{0} ".format(root.val), end="") 
+        self.preOrder(root.left) 
+        self.preOrder(root.right) 
+  
+  
+# Driver program to test above function 
+myTree = AVL_Tree() 
+root = None
+  
+root = myTree.insert(root, 10) 
+root = myTree.insert(root, 20) 
+root = myTree.insert(root, 30) 
+root = myTree.insert(root, 40) 
+root = myTree.insert(root, 50) 
+root = myTree.insert(root, 25) 
+  
+"""The constructed AVL Tree would be 
+            30 
+           /  \ 
+         20   40 
+        /  \     \ 
+       10  25    50"""
+  
+# Preorder Traversal 
+print("Preorder traversal of the", 
+      "constructed AVL tree is") 
+myTree.preOrder(root) 
+print() 
+################################
+#OUTPUT 
+#Preorder traversal of the constructed AVL tree is
+#30 20 10 25 40 50