Question

Python!

Modify the following code to include countries name which should be displaying onto the console from countries with the lowest population to the highest Morroco :38,964, china:1000000000, usa:400,000,000, England:55,000,000.   

class Node:
    def __init__(self,value):
        self.value=value
        self.right=None
        self.left=None
class BinarySearchTree:
    def __init__(self):
        self.root=None
    #adding the element to the bst
    def add(self,value):
        node=Node(value)
        temp=self.root
        flag=1
        while(temp):
            flag=0
            if(node.value>temp.value):
                if(temp.right):
                    temp=temp.right
                else:
                    temp.right=node
                    break
            else:
                if(temp.left):
                    temp=temp.left
                else:
                    temp.left=node
                    break
        if(flag):
            self.root=node
    #pre order traversing
    def preOrder(self,root):
        if(root):
            print(root.value)
            self.preOrder(root.left)
            self.preOrder(root.right)
    #in order traversing
    def inOrder(self,root):
        if(root):
            self.inOrder(root.left)
            print(root.value)
            self.inOrder(root.right)
    #post order traversing
    def postOrder(self,root):
        if(root):
            self.postOrder(root.left)
            self.postOrder(root.right)
            print(root.value)

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

Note: Please maintain proper code spacing (indentation), just copy the code part and paste it in your compiler/IDE directly, no modifications required.

#code

class Node:
    def __init__(self,value):
        self.value=value
        self.right=None
        self.left=None

class BinarySearchTree:
    def __init__(self):
        self.root=None
    #adding the element to the bst
    def add(self,value):
        node=Node(value)
        temp=self.root
        flag=1
        while(temp):
            flag=0
            #the objects need to implement __gt__() method in order to use
            #> operator to compare two values. if this is any built in data
            #types like int, str, float etc, the method is already implemented
            #but if it is a custom class, you should implement __gt__() method
            if(node.value>temp.value):
                if(temp.right):
                    temp=temp.right
                else:
                    temp.right=node
                    break
            else:
                if(temp.left):
                    temp=temp.left
                else:
                    temp.left=node
                    break
        if(flag):
            self.root=node
    
    #methods to perform the appropriate traversal by calling the appropriate recursive
    #methods
    def printPreOrder(self):
        self.preOrder(self.root)

    def printInOrder(self):
        self.inOrder(self.root)

    def printPostOrder(self):
        self.postOrder(self.root)

    #pre order traversing
    def preOrder(self,root):
        if(root):
            print(root.value)
            self.preOrder(root.left)
            self.preOrder(root.right)
    #in order traversing
    def inOrder(self,root):
        if(root):
            self.inOrder(root.left)
            print(root.value)
            self.inOrder(root.right)
    #post order traversing
    def postOrder(self,root):
        if(root):
            self.postOrder(root.left)
            self.postOrder(root.right)
            print(root.value)


''' a class to represent a Country'''
class Country:
    #constructor taking country name and population
    def __init__(self, name, population):
        #assigning values to instance variables
        self.name=name
        self.population=population
    #magic method to implement > operator operation between two Country objects
    #this is required for the above binary search tree to work with Country objects
    #if your BinarySearchTree use < operator in future, then you might want to
    #implement __lt__ operator function also (<)
    def __gt__(self, other):
        #returns True if this country's population is greater than other's
        return self.population>other.population
    #magic method to return a string containing country details. this method gets
    #invoked when a Country object is printed
    def __str__(self):
        return '{}:{}'.format(self.name,self.population)


def main():
    #creating a BinarySearchTree
    tree=BinarySearchTree()
    #adding some Country objects to it
    tree.add(Country('Morroco',38964))
    tree.add(Country('China',1000000000))
    tree.add(Country('USA',400000000))
    tree.add(Country('England',55000000))
    #printing the tree in 'in order' so that countries will be printed according
    #to increasing order of population
    tree.printInOrder()
main()