Inserting a value into a Binary Search Tree in Python

Question

I am reviewing for my final and one of the practice problem asks to implement a function that puts a value into a binary search tree in Python. Here is the Tree implementation I am using.

class Tree(object):
 def __init__(self, entry, left=None, right=None):
 self.entry = entry
 self.left = left
 self.right = right

Here is the function I need to fill in.

def insert(item, tree):
 """
 >>> t = Tree(5, Tree(1, None, Tree(4)), Tree(7, Tree(6), Tree(8)))
 >>> insert(2, t)
 >>> t
 Tree(5, Tree(1, None, Tree(4, Tree(2), None)), Tree(7, Tree(6), Tree(8)))
 """

Can anyone help me implement this code, as I have no idea where to start? Thanks!

• HennyH: Do you want the value to be put at the end of the tree?
• Rachel Gallen: stackoverflow.com/questions/5444394/…
• Jisoo Han: The value should be put in like the doctest

Answer 1

def insert(item, tree):
 if (item < tree.entry):
 if (tree.left != None):
 insert(item, tree.left)
 else:
 tree.left = Tree(item)
 else:
 if (tree.right != None):
 insert(item, tree.right)
 else:
 tree.right = Tree(item)

• Jisoo Han: Thanks! This is exactly what I was looking for. I think I got confused on the tree.left = Tree(item) and tree.right = Tree(item) part. I didn't fully understand how to insert it; however, I knew how to recurse through it.

Answer 2

Tree is a Non linear data structure.A tree is created by set of vertices and set of edges.Average searching complexity is logn . Let's consider how to insert values to tree. First of all , you would create a Vertices.In another way, you would create nodes.then , Those nodes which is created insert hierarchical manner.In creating Node class , You can initialize all the properties of Node class in constructor function.Actually like this,

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

At beginning, Node's data=data, left child of Node is None and right child of Node is None.And then , you can create a binary search tree using those created nodes.

class tree:
 def __init__(self):
 self.root=None
 def insert(self,data):
 if(self.root==None):
 self.root=Node(data)
 else:
 self._insert(data,self.root)
 def _insert(self, data, curNode):
 if(curNode.data>data):
 if(curNode.left==None):
 curNode.left=Node(data)
 else:
 self._insert(data,curNode.left)
 else:
 if(curNode.right==None):
 curNode.right=Node(data)
 else:
 self._insert(data,curNode.right)

At first, root node is initialized under constructor method of tree class.And then insert nodes using insert function.Using any tree traversal method can be printed elements of tree..I think , you could understand.thank you!