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AVL recog.py

@@ -0,0 +1,109 @@
+class TreeNode: 
+    def __init__(self, val): 
+        self.val = val 
+        self.left = None
+        self.right = None
+        self.height = 1
+
+class AVL_Tree: 
+    def __init__(self):
+        self.pre = []
+    def insert(self, root, key):  
+        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) 
+
+        root.height = 1 + max(self.getHeight(root.left), 
+                           self.getHeight(root.right)) 
+
+        balance = self.getBalance(root) 
+
+        if balance > 1 and key < root.left.val: 
+            return self.rightRotate(root) 
+
+        if balance < -1 and key > root.right.val: 
+            return self.leftRotate(root) 
+
+        if balance > 1 and key > root.left.val: 
+            root.left = self.leftRotate(root.left) 
+            return self.rightRotate(root) 
+
+        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 
+
+        y.left = z 
+        z.right = T2 
+
+        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 y 
+
+    def rightRotate(self, z): 
+        y = z.left 
+        T3 = y.right 
+
+        y.right = z 
+        z.left = T3 
+
+        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 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)
+
+    def preOrdergetlist(self, root): 
+        if not root: 
+            return
+        self.pre.append(root.val)
+        self.preOrdergetlist(root.left)
+        self.preOrdergetlist(root.right)
+
+def isAVL(tree:list):
+    myTree = AVL_Tree() 
+    root = None
+    for node in tree:
+        root = myTree.insert(root, node) 
+    myTree.preOrdergetlist(root)
+    return myTree.pre == tree
+
+
+"""The constructed AVL Tree for [10, 20, 25, 30, 40, 50] would be
+            30 
+           /  \ 
+         20   40 
+        /  \     \ 
+       10  25    50
+"""
+print(isAVL([30, 20, 10, 25, 40, 50]))
+print(isAVL([30, 20, 25, 10, 40, 50]))
+print(isAVL([1]))