impression on week 7

This week we talked about binary search tree. It is a special kind tree in which every parent node has at most two children.
                 

’’’Binary Tree node.’’’  

    def __init__(self, data, left=None, right=None):
        ’’’ (BTNode, object, BTNode, BTNode) -> NoneType

        Create BTNode (self) with data
        and children left and right.
        ’’’
        self.data, self.left, self.right = data, left, right

We have different implementations for binary search tree which 

seems not that difficult to understand since we can always refer to a graph if feeling confused. Many things told were similar to those 

talked about in last week's lectures. The new stuffs introduced were about the travelling of trees.

There are 3 orders : inorder, preorder and postorder 

1. inorder

from left to right and recursively

if root is None:
    pass
    else:
        inorder_visit(root.left, perform)
        perform(root)
        inorder_visit(root.right, perform)

2.preorder
from the root to the leaves and recursively

perform(root) 
preorder_visit(root.left, perform)
preorder_visit(root.right, perform)

3. postorder
from leaves to the root and recursively

preorder_visit(root.left, perform)
preorder_visit(root.right, perform)

perform(root)