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!

Do you want the value to be put at the end of the tree?

HennyH
– HennyH

2013-05-12 08:39:03 +00:00
Commented May 12, 2013 at 8:39 — HennyH
– HennyH, Commented May 12, 2013 at 8:39
stackoverflow.com/questions/5444394/…

Rachel Gallen
– Rachel Gallen

2013-05-12 08:56:50 +00:00
Commented May 12, 2013 at 8:56 — Rachel Gallen
– Rachel Gallen, Commented May 12, 2013 at 8:56
The value should be put in like the doctest

Jisoo Han
– Jisoo Han

2013-05-12 09:15:23 +00:00
Commented May 12, 2013 at 9:15 — Jisoo Han
– Jisoo Han, Commented May 12, 2013 at 9:15

isaach1000 · Accepted Answer · 2013-05-12 08:50:30Z

10

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)

edited May 12, 2013 at 8:50

answered May 12, 2013 at 8:41

isaach1000

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1 Comment

Jisoo Han Over a year ago

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.

Gayan Sampath · Accepted Answer · 2018-07-02 16:51:56Z

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!

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