二叉查找树的插入和遍历

数节点：

public class Node {

	private int value;			//data
	private Node leftChild;		//左孩子节点
	private Node rightChild;	//右孩子节点
	
	public Node(int value, Node leftChild, Node rightChild){
		this.value = value;
		this.leftChild = leftChild;
		this.rightChild = rightChild;
	}

	public int getValue() {
		return value;
	}

	public void setValue(int value) {
		this.value = value;
	}

	public Node getLeftChild() {
		return leftChild;
	}

	public void setLeftChild(Node leftChild) {
		this.leftChild = leftChild;
	}

	public Node getRightChild() {
		return rightChild;
	}

	public void setRightChild(Node rightChild) {
		this.rightChild = rightChild;
	}
	
}

数：

public class Tree {

	Node root;	//树的根节点
	private Node parent;
	private Node current; 	
	
	/**
	 * 插入数据
	 * @param data
	 */
	public void insertData(int data) {
		
		Node node = new Node(data, null, null); 
		
		//为空表示还没有根节点
		if(root == null) { 	
			root = node;
		}
		//插入操作，注意这里已经存在根节点了
		else {
			
			current = root;	//每次都从根开始
			
			for(;;) {
				
				if( data == current.getValue() ) {
					throw new RuntimeException("数中已经存在该数据！！！");
				}
				//往current左边插
				else if( data < current.getValue() ) {
					
					parent = current;
					current = parent.getLeftChild();
					
					if(current == null) {
						parent.setLeftChild(node);
						break;
					}
				}
				//往current右边插
				else if( data > current.getValue() ) {
					
					parent = current;
					current = parent.getRightChild();
					
					if(current == null) {
						parent.setRightChild(node);
						break;
					}
				}				
			}
		}
	}
	
	
	/**
	 * 后序遍历：左 - 右 - 中
	 * @param rootNode
	 */
	public void subsequentTraversal(Node rootNode){
		
		if(rootNode == null)
			throw new RuntimeException("rootNode不能为空");

		
		Node leftNode = rootNode.getLeftChild();
		if(leftNode != null)
			subsequentTraversal(leftNode);
		
		Node rightNode = rootNode.getRightChild();
		if(rightNode != null)
			subsequentTraversal(rightNode);
		
		System.out.print(rootNode.getValue() + "	");
	
	}
	
	
	/**
	 * 前序遍历：中 - 左 - 右
	 * @param rootNode
	 */
	public void preorderTraversal(Node rootNode){
		
		if(rootNode == null)
			throw new RuntimeException("rootNode不能为空");
		
		System.out.print(rootNode.getValue() + "	");
		
		Node leftNode = rootNode.getLeftChild();
		if(leftNode != null)
			preorderTraversal(leftNode);
		
		Node rightNode = rootNode.getRightChild();
		if(rightNode != null)
			preorderTraversal(rightNode);
		
	}
	
	
	
	/**
	 * 中序遍历：左 - 中 - 右
	 * @param rootNode
	 */
	public void inorderTraversal(Node rootNode) {

		if(rootNode == null)
			throw new RuntimeException("rootNode不能为空");
		
		Node leftNode = rootNode.getLeftChild();
		if(leftNode != null) {
			inorderTraversal(leftNode);
		}
		
		System.out.print(rootNode.getValue() + "	");
		
		Node rightNode = rootNode.getRightChild();
		if(rightNode != null) {
			inorderTraversal(rightNode);
		}
		
	}

	
}

测试：

public class Main {

	public static void main(String[] args) {
	
		Tree t = new Tree();
		
		int[] arr = {8,5,3,2,4,10};
		Arrays.stream(arr).forEach((i)->{
			t.insertData(i);
		});
		
		t.preorderTraversal(t.root); 	//前序遍历
		System.out.println();
		t.inorderTraversal(t.root); 	//中序遍历
		System.out.println();
		t.subsequentTraversal(t.root);	//后续遍历
	}

}