Merge pull request TheAlgorithms#200 from pablo9891/master

Added delete function to binary_search_tree.py and print function

Author: harshildarji

data_structures/Binary Tree/binary_search_tree.py

@@ -1,13 +1,14 @@
 '''
 A binary search Tree
 '''
-
 class Node:
 
-    def __init__(self, label):
+    def __init__(self, label, parent):
         self.label = label
         self.left = None
         self.right = None
+        #Added in order to delete a node easier
+        self.parent = parent
 
     def getLabel(self):
         return self.label
@@ -27,6 +28,11 @@ def getRight(self):
     def setRight(self, right):
         self.right = right
 
+    def getParent(self):
+        return self.parent
+
+    def setParent(self, parent):
+        self.parent = parent
 
 class BinarySearchTree:
 
@@ -35,13 +41,12 @@ def __init__(self):
 
     def insert(self, label):
         # Create a new Node
-        new_node = Node(label)
+        new_node = Node(label, None)
         # If Tree is empty
         if self.empty():
             self.root = new_node
         else:
             #If Tree is not empty
-            parent_node = None
             curr_node = self.root
             #While we don't get to a leaf
             while curr_node is not None:
@@ -58,7 +63,34 @@ def insert(self, label):
             if new_node.getLabel() < parent_node.getLabel():
                 parent_node.setLeft(new_node)
             else:
-                parent_node.setRight(new_node)        
+                parent_node.setRight(new_node)
+            #Set parent to the new node
+            new_node.setParent(parent_node)      
+    
+    def delete(self, label):
+        if (not self.empty()):
+            #Look for the node with that label
+            node = self.getNode(label)
+            #If the node exists
+            if(node is not None):
+                #If it has no children
+                if(node.getLeft() is None and node.getRight() is None):
+                    self.__reassignNodes(node, None)
+                    node = None
+                #Has only right children
+                elif(node.getLeft() is None and node.getRight() is not None):
+                    self.__reassignNodes(node, node.getRight())
+                #Has only left children
+                elif(node.getLeft() is not None and node.getRight() is None):
+                    self.__reassignNodes(node, node.getLeft())
+                #Has two children
+                else:
+                    #Gets the max value of the left branch
+                    tmpNode = self.getMax(node.getLeft())
+                    #Deletes the tmpNode
+                    self.delete(tmpNode.getLabel())
+                    #Assigns the value to the node to delete and keesp tree structure
+                    node.setLabel(tmpNode.getLabel())
 
     def getNode(self, label):
         curr_node = None
@@ -78,45 +110,121 @@ def getNode(self, label):
                     curr_node = curr_node.getRight()
         return curr_node
 
+    def getMax(self, root = None):
+        if(root is not None):
+            curr_node = root
+        else:
+            #We go deep on the right branch
+            curr_node = self.getRoot()
+        if(not self.empty()):
+            while(curr_node.getRight() is not None):
+                curr_node = curr_node.getRight()
+        return curr_node
+
+    def getMin(self, root = None):
+        if(root is not None):
+            curr_node = root
+        else:
+            #We go deep on the left branch
+            curr_node = self.getRoot()
+        if(not self.empty()):
+            curr_node = self.getRoot()
+            while(curr_node.getLeft() is not None):
+                curr_node = curr_node.getLeft()
+        return curr_node
+
     def empty(self):
         if self.root is None:
             return True
         return False
 
-    def preShow(self, curr_node):
+    def __InOrderTraversal(self, curr_node):
+        nodeList = []
         if curr_node is not None:
-            print(curr_node.getLabel())
-            self.preShow(curr_node.getLeft())
-            self.preShow(curr_node.getRight())
+            nodeList.insert(0, curr_node)
+            nodeList = nodeList + self.__InOrderTraversal(curr_node.getLeft())
+            nodeList = nodeList + self.__InOrderTraversal(curr_node.getRight())
+        return nodeList
 
     def getRoot(self):
         return self.root
 
-'''
-Example
-            8
-           / \
-          3   10
-         / \    \
-        1   6    14
-           / \   /
-          4   7 13 
-'''
+    def __isRightChildren(self, node):
+        if(node == node.getParent().getRight()):
+            return True
+        return False
 
+    def __reassignNodes(self, node, newChildren):
+        if(newChildren is not None):
+            newChildren.setParent(node.getParent())
+        if(node.getParent() is not None):
+            #If it is the Right Children
+            if(self.__isRightChildren(node)):
+                node.getParent().setRight(newChildren)
+            else:
+                #Else it is the left children
+                node.getParent().setLeft(newChildren)
 
-if __name__ == "__main__":
+    #This function traversal the tree. By default it returns an
+    #In order traversal list. You can pass a function to traversal
+    #The tree as needed by client code
+    def traversalTree(self, traversalFunction = None, root = None):
+        if(traversalFunction is None):
+            #Returns a list of nodes in preOrder by default
+            return self.__InOrderTraversal(self.root)
+        else:
+            #Returns a list of nodes in the order that the users wants to
+            return traversalFunction(self.root)
+
+    #Returns an string of all the nodes labels in the list 
+    #In Order Traversal
+    def __str__(self):
+        list = self.__InOrderTraversal(self.root)
+        str = ""
+        for x in list:
+            str = str + " " + x.getLabel().__str__()
+        return str
+
+def InPreOrder(curr_node):
+    nodeList = []
+    if curr_node is not None:
+        nodeList = nodeList + InPreOrder(curr_node.getLeft())
+        nodeList.insert(0, curr_node.getLabel())
+        nodeList = nodeList + InPreOrder(curr_node.getRight())
+    return nodeList
+
+def testBinarySearchTree():
+    '''
+    Example
+                  8
+                 / \
+                3   10
+               / \    \
+              1   6    14
+                 / \   /
+                4   7 13 
+    '''
+
+    '''
+    Example After Deletion
+                  7
+                 / \
+                1   4
+
+    '''
     t = BinarySearchTree()
     t.insert(8)
     t.insert(3)
-    t.insert(1)
     t.insert(6)
-    t.insert(4)
-    t.insert(7)
+    t.insert(1)
     t.insert(10)
     t.insert(14)
     t.insert(13)
+    t.insert(4)
+    t.insert(7)
 
-    t.preShow(t.getRoot())
+    #Prints all the elements of the list in order traversal
+    print(t.__str__())
 
     if(t.getNode(6) is not None):
         print("The label 6 exists")
@@ -128,3 +236,22 @@ def getRoot(self):
     else:
         print("The label -1 doesn't exist")
 
+    if(not t.empty()):
+        print("Max Value: ", t.getMax().getLabel())
+        print("Min Value: ", t.getMin().getLabel())
+    
+    t.delete(13)
+    t.delete(10)
+    t.delete(8)
+    t.delete(3)
+    t.delete(6)
+    t.delete(14)
+
+    #Gets all the elements of the tree In pre order
+    #And it prints them
+    list = t.traversalTree(InPreOrder, t.root)
+    for x in list:
+        print(x)
+
+if __name__ == "__main__":
+    testBinarySearchTree()