Binary Tree

Uses

DOM (Document Object Model)
Social Media Comments
AST (Abstract Syntax Tree)

Properties

Each Node can have only 0,1 or 2 Nodes only
Each Child can only have one parent
Tree DS does not have any loops

Perfect Binary Tree
On each level the no. of nodes double
Nodes on last level = Nodes on other level + 1
No. of Nodes on a level = $2^h-1$, where h is level
Half of the nodes of the Perfect Binary Tree are always at the last level

Types

Perfect Binary Tree

All the terminal nodes have 2 children and all leaf nodes are at the same level

           18
       /       \  
     15         30  
    /  \        /  \
  40    50    100   40

Full Binary Tree

Every node has 0 or 2 children

         18
       /    \   
     15      20    
    /  \       
   40   50   
  /  \
 30  50

Complete Binary Tree

All levels are completely filled except possibly the last level and the last level has all keys as left as possible

            18
       /         \  
     15           30  
    /  \         /  \
  40    50     100   40
 /  \   /
8   7  9