Java二叉树的递归，非递归遍历，高度，节点数，叶子节点数

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

public class Main {
      public static class TreeNode<T>{
    	 T data;
    	 TreeNode<T> left=null;
    	 TreeNode<T> right=null;

    	public TreeNode() {}
    	public TreeNode(T data){
 			this.data=data;
 		}
		public TreeNode(T data, TreeNode left, TreeNode right) {
			super();
			this.data = data;
			this.left = left;
			this.right = right;
		}
     }

      public static class BinaryTree<T>{
    	  /**二叉树的根节点*/
    	  private TreeNode<T> root;

    	  public BinaryTree(){}
    	  public BinaryTree(TreeNode<T> root){
    	    this.root = root;
    	  }

    	 /* public TreeNode<Integer> createBinaryTree(){
    		  TreeNode<Integer> e = new   TreeNode<Integer>(5);
    		  TreeNode<Integer> g = new   TreeNode<Integer>(7);
    		  TreeNode<Integer> h = new   TreeNode<Integer>(8);

    		  TreeNode<Integer> l = new   TreeNode<Integer>(12);
    		  TreeNode<Integer> m = new   TreeNode<Integer>(13);
    		  TreeNode<Integer> n = new   TreeNode<Integer>(14);
    		  TreeNode<Integer> k = new   TreeNode<Integer>(11, n, null);
    		  TreeNode<Integer> j = new   TreeNode<Integer>(10, l, m);
    		  TreeNode<Integer> i = new   TreeNode<Integer>(9, j, k);
    		  TreeNode<Integer> d = new   TreeNode<Integer>(4, null, g);

    		  TreeNode<Integer> f = new   TreeNode<Integer>(6, h, i);
    		  TreeNode<Integer> b = new   TreeNode<Integer>(2, d, e);
    		  TreeNode<Integer> c = new   TreeNode<Integer>(3, f, null);

    		  TreeNode<Integer> root = new   TreeNode<Integer>(1, b, c);
    		  return root;
    	  }*/
    	  //递归前序
    	  public void preOrder(TreeNode<T> root){
    		  if(root!=null){
    			  visit(root);
    			  preOrder(root.left);
    			  preOrder(root.right);
    		  }
    	  }
    	  /*非递归前序:对于任一结点P：

    	     1)访问结点P，并将结点P入栈;

    	     2)判断结点P的左孩子是否为空，若为空，则取栈顶结点并进行出栈操作，并将栈顶结点的右孩子置为当前的结点P，循环至1);若不为空，则将P的左孩子置为当前的结点P;

    	     3)直到P为NULL并且栈为空，则遍历结束。
    	     */
    	  public void nonRecursivePreOrder(TreeNode<T> root){
    		  Stack<TreeNode<T>> s=new Stack<TreeNode<T>>();
    		  if(root!=null){
    			  s.push(root);//先把根节点入栈
    			  while(!s.isEmpty()){//while栈不为空
    				  TreeNode<T> node=s.pop();//弹出栈
    				  visit(node);
    				  if(node.right!=null) s.push(node.right);//把右节点入栈
    				  if(node.left!=null)  s.push(node.left); //把左节点入栈
    			  }

    		  }
    	  }

    	  //递归中序
          public void inOrder(TreeNode<T> root){
        	  if(root!=null){

    			  inOrder(root.left);
    			  visit(root);
    			  inOrder(root.right);
    		  }
          }
          //非递归中序遍历：对于任一结点P，将其入栈，然后沿其左子树一直往下搜索，直到搜索到没有左孩子的结点，此时该结点出现在栈顶，
          //但是此时不能将其出栈并访问，因此其右孩子还为被访问。所以接下来按照相同的规则对其右子树进行相同的处理，当访问完其右孩子时，该结点又出现在栈顶，此时可以将其出栈并访问。
          public void nonRecursiveInOrder(TreeNode<T> root){
        	  Stack<TreeNode<T>> stack=new Stack<TreeNode<T>>();
        	  TreeNode<T> node=root;
        	  while(node!=null||!stack.isEmpty()){
        		  //左子树一直入栈
        		  while(node!=null){//一直找到节点左子树是空的节点
        			  stack.push(node);
        			  node=node.left;
        		  }

        		  node=stack.pop();//左子树是空的就是访问这个节点
        		  visit(node);
        		  node=node.right;//在找该节点的右子树
        	  }
          }
          //递归后序
          public void postOrder(TreeNode<T> root){
        	  if(root!=null){
    			  postOrder(root.left);
    			  postOrder(root.right);
    			  visit(root);
    		  }
          }
          //非递归后序遍历
          public void nonRecursivePostOrder(TreeNode<T> root){
        	  TreeNode<T> node=root;
        	  TreeNode<T> preNode=null;//记录之前遍历的右结点
        	  Stack<TreeNode<T>> stack=new Stack<TreeNode<T>>();
        	  while(node!=null||!stack.isEmpty()){
        		  /*左子树一直入栈*/
        		  while(node!=null){
        			  stack.push(node);
        			  node=node.left;
        		  }
        		  node=stack.peek();//获得栈顶节点但不出栈

        		  /*如果右结点为空，或者右结点之前遍历过，打印根结点*/
        		  if(node.right==null||node.right==preNode){
        			  visit(node);
        			  node=stack.pop();
        			  preNode = node;
        			  node=null;
        		  }
        		  else{
        			  node=node.right;
        		  }

        	  }

          }
          //层次遍历
          public void levelTraverse(TreeNode<T> root){
        	  //Queue是一个接口，不能直接实例化，一般使用它的实现类LinkedList当做队列用，
        	  //Queue的实现类还有LinkedList, PriorityQueue, LinkedBlockingQueue, BlockingQueue, ArrayBlockingQueue, LinkedBlockingQueue, PriorityBlockingQueue
        	  Queue<TreeNode<T>> queue=new LinkedList<TreeNode<T>>();
        	  TreeNode<T> node=root;
        	  queue.offer(node);//队列用offer添加元素

        	  /*对每一个节点先出队列再让其左节点和右节点入队列*/
        	  while(!queue.isEmpty()){
        		  node=queue.poll();//队列用poll出队列
        		  if(node!=null){
        			  visit(node);
        			  //左右节点入队列
        			  queue.offer(node.left);
        			  queue.offer(node.right);
        		  }

        	  }
          }
          //递归求树的高度
          public int treeHeight(TreeNode<T> root){
        	  if(root==null){
        		  return 0;
        	  }
        	  else{
        		  int leftTreeHeight=treeHeight(root.left);
        		  int rightTreeHeight=treeHeight(root.right);
        		  return leftTreeHeight>rightTreeHeight?leftTreeHeight+1:rightTreeHeight+1;
        	  }
          }
         //递归求节点总数
          public int treeNodes(TreeNode<T> root){
        	  if(root==null){
        		  return 0;
        	  }
        	  else{
        		  int leftTreeNodes=treeNodes(root.left);
        		  int rightTreeNodes=treeNodes(root.right);
        		  return leftTreeNodes+rightTreeNodes+1;
        	  }
          }
          //递归求叶子节点总数
          public int treeLeaf(TreeNode<T> root){
        	  if(root==null){
        		  return 0;
        	  }
        	  else{
        		  int leftTreeLeaf=treeLeaf(root.left);
        		  int rightTreeLeaf=treeLeaf(root.right);
        		  if(root.left==null&&root.right==null){
        			  return leftTreeLeaf+rightTreeLeaf+1;
        		  }
        		  else{
        			  return leftTreeLeaf+rightTreeLeaf;
        		  }
        	  }
          }
          public void visit(TreeNode<T> root) {
			System.out.print(root.data+" ");
	      }

      }

      public static void main(String[] args) {
    	  TreeNode<Integer> e = new   TreeNode<Integer>(5);
		  TreeNode<Integer> g = new   TreeNode<Integer>(7);
		  TreeNode<Integer> h = new   TreeNode<Integer>(8);

		  TreeNode<Integer> l = new   TreeNode<Integer>(12);
		  TreeNode<Integer> m = new   TreeNode<Integer>(13);
		  TreeNode<Integer> n = new   TreeNode<Integer>(14);
		  TreeNode<Integer> k = new   TreeNode<Integer>(11, n, null);
		  TreeNode<Integer> j = new   TreeNode<Integer>(10, l, m);
		  TreeNode<Integer> i = new   TreeNode<Integer>(9, j, k);
		  TreeNode<Integer> d = new   TreeNode<Integer>(4, null, g);

		  TreeNode<Integer> f = new   TreeNode<Integer>(6, h, i);
		  TreeNode<Integer> b = new   TreeNode<Integer>(2, d, e);
		  TreeNode<Integer> c = new   TreeNode<Integer>(3, f, null);

		  TreeNode<Integer> root = new   TreeNode<Integer>(1, b, c);

		  BinaryTree<Integer> tree=new BinaryTree<Integer>(root);
		  System.out.println("递归前序遍历二叉树结果：");
		  tree.preOrder(root);
		  System.out.println();
		  System.out.println("非递归前序遍历二叉树结果：");
		  tree.nonRecursivePreOrder(root);
		  System.out.println();

		  System.out.println("递归中序遍历二叉树结果：");
		  tree.inOrder(root);
		  System.out.println();
		  System.out.println("非递归中序遍历二叉树结果：");
		  tree.nonRecursiveInOrder(root);
		  System.out.println();

		  System.out.println("递归后序遍历二叉树结果：");
		  tree.postOrder(root);
		  System.out.println();
		  System.out.println("非递归后序遍历二叉树结果：");
		  tree.nonRecursivePostOrder(root);
		  System.out.println();

		  System.out.println("层次遍历二叉树结果：");
		  tree.levelTraverse(root);
		  System.out.println();

		  System.out.println("递归求二叉树的高度："+ tree.treeHeight(root));

		  System.out.println("递归二叉树的结点数："+ tree.treeNodes(root));

		  System.out.println("递归二叉树的叶子节点："+tree.treeLeaf(root));

      }
}

输出

递归前序遍历二叉树结果：
1 2 4 7 5 3 6 8 9 10 12 13 11 14
非递归前序遍历二叉树结果：
1 2 4 7 5 3 6 8 9 10 12 13 11 14
递归中序遍历二叉树结果：
4 7 2 5 1 8 6 12 10 13 9 14 11 3
非递归中序遍历二叉树结果：
4 7 2 5 1 8 6 12 10 13 9 14 11 3
递归后序遍历二叉树结果：
7 4 5 2 8 12 13 10 14 11 9 6 3 1
非递归后序遍历二叉树结果：
7 4 5 2 8 12 13 10 14 11 9 6 3 1
层次遍历二叉树结果：
1 2 3 4 5 6 7 8 9 10 11 12 13 14
递归求二叉树的高度：6
递归二叉树的结点数：14
递归二叉树的叶子节点：6