diff --git a/data_structures/binary tree/AVLtree.py b/data_structures/binary tree/AVLtree.py
index cd867906f..c0b37ab08 100644
--- a/data_structures/binary tree/AVLtree.py	
+++ b/data_structures/binary tree/AVLtree.py	
@@ -3,6 +3,7 @@
 An auto-balanced binary tree!
 '''
 import math
+import random
 class my_queue:
     def __init__(self):
         self.data = []
@@ -65,6 +66,7 @@ def my_max(a,b):
 
 
 def leftrotation(node):
+    print("left rotation node:",node.getdata())
     ret = node.getleft()
     node.setleft(ret.getright())
     ret.setright(node)
@@ -75,6 +77,7 @@ def leftrotation(node):
     return ret
 
 def rightrotation(node):
+    print("right rotation node:",node.getdata())
     ret = node.getright()
     node.setright(ret.getleft())
     ret.setleft(node)
@@ -113,6 +116,52 @@ def insert_node(node,data):
     node.setheight(h1)
     return node
 
+def getRightMost(root):
+    while root.getright() is not None:
+        root = root.getright()
+    return root.getdata()
+def getLeftMost(root):
+    while root.getleft() is not None:
+        root = root.getleft()
+    return root.getdata()
+
+def del_node(root,data):
+    if root.getdata() == data:
+        if root.getleft() is not None and root.getright() is not None:
+            temp_data = getLeftMost(root.getright())
+            root.setdata(temp_data)
+            root.setright(del_node(root.getright(),temp_data))
+        elif root.getleft() is not None:
+            root = root.getleft()
+        else:
+            root = root.getright()
+    elif root.getdata() > data:
+        if root.getleft() is None:
+            print("No such data")
+            return root
+        else:
+            root.setleft(del_node(root.getleft(),data))
+    elif root.getdata() < data:
+        if root.getright() is None:
+            return root
+        else:
+            root.setright(del_node(root.getright(),data))
+    if root is None:
+        return root
+    if getheight(root.getright()) - getheight(root.getleft()) == 2:
+        if getheight(root.getright().getright()) > getheight(root.getright().getleft()):
+            root = rightrotation(root)
+        else:
+            root = lrrotation(root)
+    elif getheight(root.getright()) - getheight(root.getleft()) == -2:
+        if getheight(root.getleft().getleft()) > getheight(root.getleft().getright()):
+            root = leftrotation(root)
+        else:
+            root = rlrotation(root)
+    height = my_max(getheight(root.getright()),getheight(root.getleft())) + 1
+    root.setheight(height)
+    return root
+
 class AVLtree:
     def __init__(self):
         self.root = None
@@ -120,27 +169,43 @@ class AVLtree:
 #        print("yyy")
         return getheight(self.root)
     def insert(self,data):
+        print("insert:"+str(data))
         self.root = insert_node(self.root,data)
+        
+    def del_node(self,data):
+        print("delete:"+str(data))
+        if self.root is None:
+            print("Tree is empty!")
+            return
+        self.root = del_node(self.root,data)
     def traversale(self):
         q = my_queue()
         q.push(self.root)
         layer = self.getheight()
+        if layer == 0:
+            return
         cnt = 0
         while not q.isEmpty():
             node = q.pop()
-            space = " "*int(math.pow(2,layer) - 1)
-            print(space,end = " ")
+            space = " "*int(math.pow(2,layer-1))
+            print(space,end = "")
             if node is None:
-                print("*",end = " ")
+                print("*",end = "")
+                q.push(None)
+                q.push(None)
             else:
-                print(node.getdata(),end = " ")
+                print(node.getdata(),end = "")
                 q.push(node.getleft())
                 q.push(node.getright())
-            print(space,end = " ")
+            print(space,end = "")
             cnt = cnt + 1
             for i in range(100):
                 if cnt == math.pow(2,i) - 1:
                     layer = layer -1 
+                    if layer == 0:
+                        print()
+                        print("*************************************")
+                        return
                     print()
                     break
         print()
@@ -168,27 +233,59 @@ if __name__ == "__main__":
     t = AVLtree()
     t.traversale()
 #    t.insert(7)
+##    t.traversale()
+#    
+#    t.insert(8)
 #    t.traversale()
+#    t.insert(3)
+#    t.traversale()
+#    t.insert(6)
+#    t.traversale()
+#    t.insert(1)
+#    t.traversale()
+#    t.insert(10)
+#    t.traversale()
+#    t.insert(14)
+#    t.traversale()
+#    t.insert(13)
+#    t.traversale()
+##    t.traversale()
+#    t.insert(4)
+#    t.traversale()
+#    t.insert(7)
+#    t.traversale()
+#    
+#    
+#    t.del_node(8)
+#    t.traversale()
+#    t.del_node(3)
+#    t.traversale()
+#    t.del_node(6)
+#    t.traversale()
+#    t.del_node(1)
+#    t.traversale()
+#    t.del_node(10)
+#    t.traversale()
+#    t.del_node(14)
+#    t.traversale()
+#    t.del_node(13)
+#    t.traversale()
+##    t.traversale()
+#    t.del_node(4)
+#    t.traversale()
+#    t.del_node(7)
+#    t.traversale()
+    l = list(range(10))
+    random.shuffle(l)
+    for i in l:
+        t.insert(i)
+        t.traversale()
+        
+    random.shuffle(l)
+    for i in l:
+        t.del_node(i)
+        t.traversale()
     
-    t.insert(8)
-    t.traversale()
-    t.insert(3)
-    t.traversale()
-    t.insert(6)
-    t.traversale()
-    t.insert(1)
-    t.traversale()
-    t.insert(10)
-    t.traversale()
-    t.insert(14)
-    t.traversale()
-    t.insert(13)
-    t.traversale()
-#    t.traversale()
-    t.insert(4)
-    t.traversale()
-    t.insert(7)
-    t.traversale()