Sandhya.Kishan

 Profile Answers by Sandhya.Kishan 

• Apr 7th, 2012

 

Code
 public void preorder( ) {


    if( root == null ) return;


 


    Stack<Node> stack = new Stack<Node>( );


    stack.push( root );


 


    while( ! stack.isEmpty( ) ) {


        Node current = stack.pop( );


        if( current.right != null ) stack.push( current.right );


        if( current.left != null ) stack.push( current.left );


        System.out.print( current.data + " " );


    }


}


 


/** Iteratively traverses the binary tree in in-order */


public void inorder( ) {


    Node node = root;


    Stack<Node> stack = new Stack<Node>( );


    while( ! stack.isEmpty( ) || node != null ) {


        if( node != null ) {


            stack.push( node );


            node = node.left;


        } else {


            node = stack.pop( );


            System.out.print( node.data + " " );


            node = node.right;


        }


    }


}


 


/** Iteratively traverses the binary tree in post-order */


public void postorder( ) {


    if( root == null ) return;


 


    Stack<Node> stack = new Stack<Node>( );


    Node current = root;


 


    while( true ) {


 


        if( current != null ) {


            if( current.right != null ) stack.push( current.right );


            stack.push( current );


            current = current.left;


            continue;


        }


 


        if( stack.isEmpty( ) ) return;


        current = stack.pop( );


 


        if( current.right != null && ! stack.isEmpty( ) && current.right == stack.peek( ) ) {


            stack.pop( );


            stack.push( current );


            current = current.right;


        } else {


            System.out.print( current.data + " " );


            current = null;


        }


    }


}