数据结构与算法——二叉树遍历

首先定义一个二叉树结构如下

 

class BNode{
	private String name;
	private BNode left,right;
	
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
	public BNode getLeft() {
		return left;
	}

	public void setLeft(BNode left) {
		this.left = left;
	}

	public BNode getRight() {
		return right;
	}

	public void setRight(BNode right) {
		this.right = right;
	}

	public BNode(String name)
	{
		this(name,null,null);
	}
	
	public BNode(String name,BNode left,BNode right){
		this.name = name;
		this.left = left;
		this.right = right;
	}
}

 插入一堆节点

 

BNode root;
		
root = new BNode("贾母");
root.setLeft(new BNode("贾政"));
root.setRight(new BNode("贾赦"));
root.getLeft().setLeft(new BNode("贾元春"));
root.getLeft().setRight(new BNode("贾宝玉"));
root.getRight().setLeft(new BNode("贾琏"));
root.getRight().setRight(new BNode("王熙凤"));

 下面是简单的前序遍历，中序遍历，后序遍历

 

	protected static void preOrder(BNode n)
	{
		if(n!=null){
			System.out.println(n.getName());
			preOrder(n.getLeft());
			preOrder(n.getRight());
		}
	}
	protected static void inOrder(BNode n)
	{
		if(n!=null){
			inOrder(n.getLeft());
			System.out.println(n.getName());
			inOrder(n.getRight());
		}
	}
	protected static void postOrder(BNode n)
	{
		if(n!=null){
			postOrder(n.getLeft());
			postOrder(n.getRight());
			System.out.println(n.getName());
		}
	}

 下面是广度优先遍历

 

	protected static void wideOrder(BNode n)
	{
		LinkedList l = new LinkedList();
		if(n!= null){
			l.push(n);
		}
		
		while(!l.isEmpty()){
			BNode t = (BNode)l.removeLast();
			System.out.println(t.getName());
			
			if(t.getLeft()!=null){
				l.push(t.getLeft());
			}
			if(t.getRight()!=null){
				l.push(t.getRight());
			}
		}
	}

1，首先将根节点放到队列中；

2，不断循环取队列尾，如果能取到节点，进行步骤3，否则退出循环；

3，依次将该节点的左右子节点插入队列头

下面是非递归先序遍历二叉树的一种实现，用到Stack这种数据结构，注意压栈时先右子节点后左子节点

 

	protected static void preOrder(BNode n)
	{
		Stack s = new Stack();
		
		if(n!=null){
			s.push(n);
		}		
		
		while(!s.isEmpty())
		{
			n = (BNode)s.pop();
			System.out.println(n.getName());
			if(n.getRight() != null){
				s.push(n.getRight());
			}
			if(n.getLeft()!=null){
				s.push(n.getLeft());
			}
		}
	}