Find top three elements of binary tree in python

Python program for Find top three elements of binary tree. Here mentioned other language solution.

#  Python 3 program for
#  Find top three elements in binary tree

#  Node of Binary Tree
class TreeNode :
    def __init__(self, data) :
        #  Set node value
        self.data = data
        self.left = None
        self.right = None
class BinaryTree :
    def __init__(self) :
        #  Set initial tree root to null
        self.root = None
        #  This is initial resultant Node
        self.first = None
        self.second = None
        self.third = None
    #  Recursive function
    #  Display preorder view of binary tree
    def preOrder(self, node) :
        if (node != None) :
            # Print node value
            print(" ",node.data, end ="")
            self.preOrder(node.left)
            self.preOrder(node.right)
    #  Find top three largest nodes in binary tree
    def getTopThree(self, node) :
        if (node != None) :
            if (self.first == None) :
                #  First node of tree
                self.first = node
            elif (self.first.data < node.data) :
                #  When get new first largest node
                #  Interchange the node values
                self.third = self.second
                self.second = self.first
                self.first = node
            elif (self.second == None) :
                if (self.first.data != node.data) :
                    #  Get second largest node
                    self.second = node
            else :
                if (self.second.data < node.data and 
                    self.first.data > node.data) :
                    #  When we get new second largest
                    #  Replace the third node with the second node
                    self.third = self.second
                    #  This is new second largest element
                    self.second = node
                elif (self.third == None) :
                    if (self.second.data > node.data and 
                        self.first.data > node.data) :
                        #  Get the third largest node
                        self.third = node
                elif (self.third.data < node.data and 
                      self.first.data > node.data and 
                      self.second.data > node.data) :
                    self.third = node
            #  Recursively, execute left and right subtree
            self.getTopThree(node.left)
            self.getTopThree(node.right)
    #  This are handle the request to finding
    #  top three nodes in binary tree.
    def printTopThree(self) :
        if (self.root == None) :
                return
        #  Display tree elements
        print("\n Preorder : ", end ="")
        self.preOrder(self.root)
        #  Set the initial all three nodes
        self.first = None
        self.second = None
        self.third = None
        #  Find three largest element
        self.getTopThree(self.root)
        #  Display calculated result
        print("\n First : " + str(self.first.data))
        if (self.second != None and 
            self.second != self.first and 
            self.second.data < self.first.data) :
            print(" Second : " + str(self.second.data))
        else :
            print(" Second : None ")
        if (self.third != None and 
            self.third != self.second and 
            self.third != self.first and 
            self.third.data < self.second.data) :
            print(" Third :",self.third.data)
        else :
            print(" Third : None")
    @staticmethod
    def main() :
        #  Create two trees
        x = BinaryTree()
        y = BinaryTree()
        #    Construct Binary Tree
        #    -----------------------
        #           10
        #          /  \
        #         /    \
        #        6      8
        #       / \    / \
        #      12  3  7   5
        #     /        \   \
        #    9         -6  13
        #  Add nodes
        x.root = TreeNode(10)
        x.root.left = TreeNode(6)
        x.root.left.left = TreeNode(12)
        x.root.right = TreeNode(8)
        x.root.right.right = TreeNode(5)
        x.root.right.left = TreeNode(7)
        x.root.right.left.right = TreeNode(-6)
        x.root.left.right = TreeNode(3)
        x.root.left.left.left = TreeNode(9)
        x.root.right.right.right = TreeNode(13)
        #    Construct Tree
        #    --------------
        #         1
        #        / \ 
        #       /   \
        #      1     2
        #     /     / \
        #    1     2   2
        #  Add second tree node
        y.root = TreeNode(1)
        y.root.left = TreeNode(1)
        y.root.right = TreeNode(2)
        y.root.right.right = TreeNode(2)
        y.root.right.left = TreeNode(2)
        y.root.left.left = TreeNode(1)
        #  Test One
        x.printTopThree()
        #  Test Two
        y.printTopThree()


if __name__=="__main__":
    BinaryTree.main()

Output

 Preorder :   10  6  12  9  3  8  7  -6  5  13
 First : 13
 Second : 12
 Third : 10

 Preorder :   1  1  1  2  2  2
 First : 2
 Second : 1
 Third : None