JAVA数据结构--二叉排序树

二叉排序树（Binary Sort Tree）又称二叉查找树。 它或者是一棵空树；或者是具有下列性质的二叉树： （1）若左子树不空，则左子树上所有结点的值均小于它的根结点的值； （2）若右子树不空，则右子树上所有结点的值均大于它的根结点的值； （3）左、右子树也分别为二叉排序树；在Java中构造二叉排序树实例如下：

// tree.java
// demonstrates binary tree
// to run this program: C>java TreeApp
import java.io.*;
import java.util.*;               // for Stack class
////////////////////////////////////////////////////////////////
class Node
{
public int iData;              // data item (key)
public double dData;           // data item
public Node leftChild;         // this node's left child
public Node rightChild;        // this node's right child

public void displayNode()      // display ourself
{
System.out.print('{');
System.out.print(iData);
System.out.print(", ");
System.out.print(dData);
System.out.print("} ");
}
}  // end class Node
////////////////////////////////////////////////////////////////
class Tree
{
private Node root;             // first node of tree

// -------------------------------------------------------------
public Tree()                  // constructor
{ root = null; }            // no nodes in tree yet
// -------------------------------------------------------------
public Node find(int key)      // find node with given key
{                           // (assumes non-empty tree)
Node current = root;               // start at root
while(current.iData != key)        // while no match,
{
if(key < current.iData)         // go left?
current = current.leftChild;
else                            // or go right?
current = current.rightChild;
if(current == null)             // if no child,
return null;                 // didn't find it
}
return current;                    // found it
}  // end find()
// -------------------------------------------------------------
public void insert(int id, double dd)
{
Node newNode = new Node();    // make new node
newNode.iData = id;           // insert data
newNode.dData = dd;
if(root==null)                // no node in root
root = newNode;
else                          // root occupied
{
Node current = root;       // start at root
Node parent;
while(true)                // (exits internally)
{
parent = current;
if(id < current.iData)  // go left?
{
current = current.leftChild;
if(current == null)  // if end of the line,
{                 // insert on left
parent.leftChild = newNode;
return;
}
}  // end if go left
else                    // or go right?
{
current = current.rightChild;
if(current == null)  // if end of the line
{                 // insert on right
parent.rightChild = newNode;
return;
}
}  // end else go right
}  // end while
}  // end else not root
}  // end insert()
// -------------------------------------------------------------
public boolean delete(int key) // delete node with given key
{                           // (assumes non-empty list)
Node current = root;
Node parent = root;
boolean isLeftChild = true;

while(current.iData != key)        // search for node
{
parent = current;
if(key < current.iData)         // go left?
{
isLeftChild = true;
current = current.leftChild;
}
else                            // or go right?
{
isLeftChild = false;
current = current.rightChild;
}
if(current == null)             // end of the line,
return false;                // didn't find it
}  // end while
// found node to delete

// if no children, simply delete it
if(current.leftChild==null &&
current.rightChild==null)
{
if(current == root)             // if root,
root = null;                 // tree is empty
else if(isLeftChild)
parent.leftChild = null;     // disconnect
else                            // from parent
parent.rightChild = null;
}

// if no right child, replace with left subtree
else if(current.rightChild==null)
if(current == root)
root = current.leftChild;
else if(isLeftChild)
parent.leftChild = current.leftChild;
else
parent.rightChild = current.leftChild;

// if no left child, replace with right subtree
else if(current.leftChild==null)
if(current == root)
root = current.rightChild;
else if(isLeftChild)
parent.leftChild = current.rightChild;
else
parent.rightChild = current.rightChild;

else  // two children, so replace with inorder successor
{
// get successor of node to delete (current)
Node successor = getSuccessor(current);

// connect parent of current to successor instead
if(current == root)
root = successor;
else if(isLeftChild)
parent.leftChild = successor;
else
parent.rightChild = successor;

// connect successor to current's left child
successor.leftChild = current.leftChild;
}  // end else two children
// (successor cannot have a left child)
return true;                                // success
}  // end delete()
// -------------------------------------------------------------
// returns node with next-highest value after delNode
// goes to right child, then right child's left descendents
private Node getSuccessor(Node delNode)
{
Node successorParent = delNode;
Node successor = delNode;
Node current = delNode.rightChild;   // go to right child
while(current != null)               // until no more
{                                 // left children,
successorParent = successor;
successor = current;
current = current.leftChild;      // go to left child
}
// if successor not
if(successor != delNode.rightChild)  // right child,
{                                 // make connections
successorParent.leftChild = successor.rightChild;
successor.rightChild = delNode.rightChild;
}
return successor;
}
// -------------------------------------------------------------
public void traverse(int traverseType)
{
switch(traverseType)
{
case 1: System.out.print("\nPreorder traversal: ");
preOrder(root);
break;
case 2: System.out.print("\nInorder traversal:  ");
inOrder(root);
break;
case 3: System.out.print("\nPostorder traversal: ");
postOrder(root);
break;
}
System.out.println();
}
// -------------------------------------------------------------
private void preOrder(Node localRoot)
{
if(localRoot != null)
{
System.out.print(localRoot.iData + " ");
preOrder(localRoot.leftChild);
preOrder(localRoot.rightChild);
}
}
// -------------------------------------------------------------
private void inOrder(Node localRoot)
{
if(localRoot != null)
{
inOrder(localRoot.leftChild);
System.out.print(localRoot.iData + " ");
inOrder(localRoot.rightChild);
}
}
// -------------------------------------------------------------
private void postOrder(Node localRoot)
{
if(localRoot != null)
{
postOrder(localRoot.leftChild);
postOrder(localRoot.rightChild);
System.out.print(localRoot.iData + " ");
}
}
// -------------------------------------------------------------
public void displayTree()
{
Stack globalStack = new Stack();
globalStack.push(root);
int nBlanks = 32;
boolean isRowEmpty = false;
System.out.println(
"......................................................");
while(isRowEmpty==false)
{
Stack localStack = new Stack();
isRowEmpty = true;

for(int j=0; j<nBlanks; j++)
System.out.print(' ');

while(globalStack.isEmpty()==false)
{
Node temp = (Node)globalStack.pop();
if(temp != null)
{
System.out.print(temp.iData);
localStack.push(temp.leftChild);
localStack.push(temp.rightChild);

if(temp.leftChild != null ||
temp.rightChild != null)
isRowEmpty = false;
}
else
{
System.out.print("--");
localStack.push(null);
localStack.push(null);
}
for(int j=0; j<nBlanks*2-2; j++)
System.out.print(' ');
}  // end while globalStack not empty
System.out.println();
nBlanks /= 2;
while(localStack.isEmpty()==false)
globalStack.push( localStack.pop() );
}  // end while isRowEmpty is false
System.out.println(
"......................................................");
}  // end displayTree()
// -------------------------------------------------------------
}  // end class Tree
////////////////////////////////////////////////////////////////
class TreeApp
{
public static void main(String[] args) throws IOException
{
int value;
Tree theTree = new Tree();

theTree.insert(50, 1.5);
theTree.insert(25, 1.2);
theTree.insert(75, 1.7);
theTree.insert(12, 1.5);
theTree.insert(37, 1.2);
theTree.insert(43, 1.7);
theTree.insert(30, 1.5);
theTree.insert(33, 1.2);
theTree.insert(87, 1.7);
theTree.insert(93, 1.5);
theTree.insert(97, 1.5);

while(true)
{
System.out.print("Enter first letter of show, ");
System.out.print("insert, find, delete, or traverse: ");
int choice = getChar();
switch(choice)
{
case 's':
theTree.displayTree();
break;
case 'i':
System.out.print("Enter value to insert: ");
value = getInt();
theTree.insert(value, value + 0.9);
break;
case 'f':
System.out.print("Enter value to find: ");
value = getInt();
Node found = theTree.find(value);
if(found != null)
{
System.out.print("Found: ");
found.displayNode();
System.out.print("\n");
}
else
System.out.print("Could not find ");
System.out.print(value + '\n');
break;
case 'd':
System.out.print("Enter value to delete: ");
value = getInt();
boolean didDelete = theTree.delete(value);
if(didDelete)
System.out.print("Deleted " + value + '\n');
else
System.out.print("Could not delete ");
System.out.print(value + '\n');
break;
case 't':
System.out.print("Enter type 1, 2 or 3: ");
value = getInt();
theTree.traverse(value);
break;
default:
System.out.print("Invalid entry\n");
}  // end switch
}  // end while
}  // end main()
// -------------------------------------------------------------
public static String getString() throws IOException
{
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(isr);
String s = br.readLine();
return s;
}
// -------------------------------------------------------------
public static char getChar() throws IOException
{
String s = getString();
return s.charAt(0);
}
//-------------------------------------------------------------
public static int getInt() throws IOException
{
String s = getString();
return Integer.parseInt(s);
}
// -------------------------------------------------------------
}  // end class TreeApp
////////////////////////////////////////////////////////////////