Data Structures and Algorithm Analysis - Computer Science at ...

Sec. 5.3 Binary Tree Node Implementations 155/** Binary tree node implementation: Pointers to children@param E The data element@param Key The associated key for the record */class BSTNode implements BinNode {private Key key;// Key for this nodeprivate E element;// Element for this nodeprivate BSTNode left; // Pointer to left childprivate BSTNode right; // Pointer to right child}/** Constructors */public BSTNode() {left = right = null; }public BSTNode(Key k, E val){ left = right = null; key = k; element = val; }public BSTNode(Key k, E val,BSTNode l, BSTNode r){ left = l; right = r; key = k; element = val; }/** Get and set the key value */public Key key() { return key; }public void setKey(Key k) { key = k; }/** Get and set the element value */public E element() { return element; }public void setElement(E v) { element = v; }/** Get and set the left child */public BSTNode left() { return left; }public void setLeft(BSTNode p) { left = p; }/** Get and set the right child */public BSTNode right() { return right; }public void setRight(BSTNode p) { right = p; }/** @return True if a leaf node, false otherwise */public boolean isLeaf(){ return (left == null) && (right == null); }Figure 5.7 A binary tree node class implementation.As an example of a tree that stores different information at the leaf and internalnodes, consider the expression tree illustrated by Figure 5.9. The expressiontree represents an algebraic expression composed of binary operators such as addition,subtraction, multiplication, and division. Internal nodes store operators,while the leaves store operands. The tree of Figure 5.9 represents the expression4x(2x + a) − c. The storage requirements for a leaf in an expression tree are quitedifferent from those of an internal node. Internal nodes store one of a small set ofoperators, so internal nodes could store a small code identifying the operator suchas a single byte for the operator’s character symbol. In contrast, leaves store variablenames or numbers, which is considerably larger in order to handle the widerrange of possible values. At the same time, leaf nodes need not store child pointers.