二叉排序树的实现

最适合用STree排序的是不可变类，不可变类的主要特征是它的对象的属性不能被修改．

public class Customer  implements Comparable<Object>{
	private final String name;
	private final int age;
...
}

二叉排序树操作的复杂度
最好情况: 完全树
最坏情况: 在二叉排序树为退化树时，add()和remove()处于最坏情况,相当于一个链表,可以通过红黑树消除最坏情况．

Iterator接口

package BinarySearchTree;

public interface Iterator<T> {
	public boolean hasNext();
	public T next();
	public void remove();
}

package BinarySearchTree;
import java.util.ConcurrentModificationException;
import java.util.NoSuchElementException;

public class STree<T> implements Cloneable {
	
	/**结点内部类*/
	private static class STNode<T> {
		T nodeValue;
		STNode<T> left, right, parent;
		
		/**结点类构造函数*/
		public STNode(T item, STNode<T> parentNode) {
			nodeValue = item;
			left = null;
			right = null;
			parent = parentNode;
		}
	}
	
	/**二叉搜索树类成员变量*/
	private STNode<T> root;
	private int treeSize;
	private int modCount;
	
	/**二叉搜索树类构造函数*/
	public STree() {
		root = null;
		treeSize = 0;
		modCount = 0;
	}
	
	/**插入方法*/
	public boolean add(T item) {
		STNode<T> t = root, parent = null, newNode;
		int orderValue = 0;
		
		// 循环终止条件在一个空的子树上
		while(t != null) {
			// 更新父结点的引用
			parent = t;
			// 比较item与当前结点的值
			orderValue = ((Comparable<T>)item).compareTo(t.nodeValue);
			// 比较item与当前结点的值,小于零往左走,否则向右走，等于零将不能插入新值
			if(orderValue == 0)
				return false;
			else if(orderValue < 0)
				t = t.left;
			else
				t = t.right;
		}
		// 创建新结点
		newNode = new STNode<T>(item, parent);
		
		// 下面几句是父结点与子结点的连接操作
		if(parent == null)
			// 这是第一个被添加的结点，使它成为根结点
			root = newNode;
		else if(orderValue < 0)
			// 连接新结点作为父结点的左孩子
			parent.left = newNode;
		else
			// 连接新结点作为父结点的右孩子
			parent.right = newNode;
		
		// 增加tree size and modCount
		treeSize++;
		modCount++;
		
		return true;
	}
	
	/**定位结点*/
	public T find(T item) {
		STNode<T> t = findNode(item);
		T value = null;
		if (t != null)
			value = t.nodeValue;
		return value;
	}
	
	private STNode<T> findNode(Object item) {
		STNode<T> t = root;
		int orderValue;
		while(t != null) {
			orderValue = ((Comparable<T>)item).compareTo(t.nodeValue);
			if(orderValue == 0)
				return t;
			else if(orderValue < 0)
				t = t.left;
			else
				t = t.right;
		}
		return null;
	}
	
	/**删除结点*/
	public boolean remove(Object item) {
		STNode<T> dNode = this.findNode(item);
		if(dNode == null)
			return false;
		removeNode(dNode);
		treeSize--;
		modCount++;
		return true;
	}
	
	private void removeNode(STNode<T> dNode) {
		if(dNode == null)
			return;
		
		// dNode: 待删除结点
		// pNode: 待删除结点的父结点
		// rNode: 待删除结点的替换结点
		STNode<T> pNode, rNode;
		
		pNode = dNode.parent;
		
		// 待删除的结点至少具有一棵空子树
		if(dNode.left == null || dNode.right == null) {
			// 找替换结点
			if(dNode.right == null)
				rNode = dNode.left;
			else
				rNode = dNode.right;
			
			if(rNode != null)
				rNode.parent = pNode;
			
			// 连接操作
			if(pNode == null)
				root = rNode;
			else if(((Comparable<T>)dNode.nodeValue).compareTo(pNode.nodeValue) < 0)
				pNode.left = rNode;
			else
				pNode.right = rNode;
		
		// 待删除的结点具有两个非空子树
		}else {
			// pOfRNode: 替换结点的父结点
			STNode<T> pOfRNode = dNode;
			
			rNode = dNode.right;
			pOfRNode = dNode;
			
			while(rNode.left != null) {
				pOfRNode = rNode;
				rNode = rNode.left;
			}
			
			dNode.nodeValue = rNode.nodeValue;
			
			if(pOfRNode == dNode)
				dNode.right = rNode.right;
			else
				pOfRNode.left = rNode.right;
			
			if(rNode.right != null)
				rNode.right.parent = pOfRNode;
			
			dNode = rNode;
		}
		dNode = null;
	}// end removeNode~
	
	/** 返回最小值*/
	public T first() {
		STNode<T> nextNode = root;
		if(nextNode == null)
			return null;
		while(nextNode.left != null)
			nextNode = nextNode.left;
		return nextNode.nodeValue;
	}
	
	/** 返回最大值*/
	public T last() {
		STNode<T> nextNode = root;
		if(nextNode == null)
			return null;
		while(nextNode.right != null)
			nextNode = nextNode.right;
		return nextNode.nodeValue;
	}
	
	/**清除树*/
	public void clear() {
		this.deleteTree(root);
		root = null;
		treeSize = 0;
	}
	
	private void deleteTree(STNode<T> t) {
		if(t != null) {
			deleteTree(t.left);
			deleteTree(t.right);
			t = null;
		}
	}
	
	public Object clone() {
		STree<T> copy = null;
		try {
			copy = (STree<T>)super.clone();
		}catch (CloneNotSupportedException cnse){
			throw new InternalError(); 
		}
		copy.root = copyTree(root);
		// return the cloned object
		return copy;
	}
	
	/**后根遍历由底向上复制一棵树*/
	private static<T> STNode<T> copyTree(STNode<T> t) {
		STNode<T> newLeft, newRight, newNode;
		
		if(t == null)
			return null;
		
		newLeft = copyTree(t.left);
		newRight = copyTree(t.right);
		
		newNode = new STNode<T>(t.nodeValue, null);
		newNode.left = newLeft;
		newNode.right = newRight;
		
		if(newLeft != null)
			newLeft.parent = newNode;
		if(newRight != null)
			newRight.parent = newNode;
		
		return newNode;
	}

	public boolean contains(Object item) {
		STNode<T> t = findNode(item);
		return (t == null) ? false : true;
	}
	
	public int size() {
		return treeSize;
	}
	
	public boolean isEmpty() {
		return treeSize == 0;
	}
	
	public Object[] toArray() {
		
		Iterator<T> iter = this.iterator();
		Object[] arr = new Object[treeSize];
		int i = 0;
		while(iter.hasNext()) {
			arr[i] = iter.next();
			i++;
		}
		return arr;
	}
	
	public String toString() {
		int i;
		String str = "[";
		Iterator<T> iter = this.iterator();
		for (i = 0; i < treeSize; i++) {
			str += iter.next();
			if(i < treeSize - 1)
				str += ", ";
		}
		str += "]";
		return str;
	}

	/**二叉搜索树跌代器的公共方法*/
	public Iterator<T> iterator() {
		return new MyIterator();
	}
	
	/**MyIterator内部类*/
	private class MyIterator implements Iterator<T> {
		private int expectedModCount = modCount;
		private STNode<T> tmp = null;
		private STNode<T> nextNode = null;

		MyIterator() {
			nextNode = root;
			if(nextNode != null) {
				while(nextNode.left != null)
					nextNode = nextNode.left;
			}
		}
		
		public boolean hasNext() {
			return nextNode != null;
		}
		
		public T next() {
			checkIteratorState();
			if(nextNode == null)
				throw new NoSuchElementException(
						"Iteration has no more elements");
			tmp = nextNode;
			STNode<T> p;
			
			if(nextNode.right != null) {
				nextNode = nextNode.right;
				while(nextNode.left != null)
					nextNode = nextNode.left;
			}else {
				p = nextNode.parent;
				while(p != null && nextNode == p.right) {
					nextNode = p;
					p = p.parent;
				}
				nextNode = p;
			}
			
			return tmp.nodeValue;
		}
		
		public void remove()
	      {
	         // check for a missing call to next() or previous()
	         if (tmp == null)
	            throw new IllegalStateException(
	               "Iterator call to next() " +
	               "required before calling remove()");

	         // make sure our state is good
	         checkIteratorState();

				// if lastReturned has two children, the replacement node
				// during deletion is nextNode. the value in nextNode
				// is copied to lastReturned. nextNode must be
				// lastReturned
				if (tmp.left != null && tmp.right != null)
					 nextNode = tmp;
	         removeNode(tmp);

	         // list has been modified
	         modCount++;
	         expectedModCount = modCount;

	         // we did a deletion. indicate this by setting lastReturned
	         // to null and decrementing treeSize
	         tmp = null;
	         treeSize--;
	      }
		
		 private void checkIteratorState() {
	         if (expectedModCount != modCount)
	            throw new ConcurrentModificationException(
	               "Inconsistent iterator");
		 }
		 
	}//end MyIterator~

}//end STree~

测试类

package BinarySearchTree;

// 要实现Comparable接口,然后重写compareTo方法
public class Customer  implements Comparable<Object>{
	private String name;
	private int age;
	
	public Customer(String name, int age) {
		this.name = name;
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public int getAge() {
		return age;
	}
	
	public void setName(String name) {
		this.name = name;
	}

	public void setAge(int age) {
		this.age = age;
	}
	
	public int compareTo(Object o) {
		Customer other = (Customer)o;
		
		if(this.name.compareTo(other.name) > 0)
			return 1;
		if(this.name.compareTo(other.name) < 0)
			return -1;
		
		if(this.age > other.age)
			return 1;
		if(this.age < other.age)
			return -1;
		return 0;
	}

	public static void main(String[] args) {
		STree<Customer> sT = new STree<Customer>();
		Customer c1 = new Customer("Tom", 32);
		Customer c2 = new Customer("Jack", 12);
		Customer c3 = new Customer("Lucy", 22);
		sT.add(c1); sT.add(c1);
		sT.add(c2);
		sT.add(c3);
		Iterator<Customer> it = sT.iterator();
		while(it.hasNext()) {
			Customer c = it.next();
			System.out.println(c.getName() + " " + c.getAge());
		}
		
		Customer minAge = sT.first();
		System.out.println("minAge: " + minAge.getName() + " " + minAge.getAge());
		
		Customer f = sT.find(c2);
		f.setAge(42);
		System.out.println("find: " + f.getName() + " " + f.getAge());
		
		System.out.println(sT.contains(c3));
		
		sT.clear();
		System.out.println(sT.size());
	}

	

	

}