创建一个二叉树对象

 private static class Node{
        int data;
        Node leftNode;
        Node righNode;
        public Node(int data, Node leftNode, Node righNode) {
            super();
            this.data = data;
            this.leftNode = leftNode;
            this.righNode = righNode;
        }
        public int getData() {
            return data;
        }
        public void setData(int data) {
            this.data = data;
        }
        public Node getLeftNode() {
            return leftNode;
        }
        public void setLeftNode(Node leftNode) {
            this.leftNode = leftNode;
        }
        public Node getRighNode() {
            return righNode;
        }
        public void setRighNode(Node righNode) {
            this.righNode = righNode;
        }
        
    }

build 一个二叉树

private static Node rootNode;
public static void buildTree(int[] A){
    for(int i:A){
        rootNode = insertData(rootNode,i);
    }
}

public static void insertData(Node tree, int a){
    if (tree == null){
          return new Node(a, 0, 0);
    }
  
  if (a>tree.getData()){
      return tree.setRightNode(insertData(tree.getRightNode(), a));
  } else {
      return tree.setLeftNode(insertData(tree.getLeftNode(),a));
  }
}

遍历

先序遍历

public static void preOrder(Node node){
    if (node!=null){
        System.out.println(node.getData());
        preOrder(node.getLeftNode());
        preOrder(node.getRightNode());
    }
}

后序遍历

public static void postOrder(Node node){
    if (node != null ){
        postOrder(node.getLeftNode())；
        postOrder(node.getRightNode());
       System.out.println(node.getData());
    }
}

中序遍历

public static void inOrder(Node node){
    if (node!=null){
          inOrder(node.getLeftNode());
          System.out.println(node.getData());
          inOrder(node.getRightNode());
    }
}

image.png

先序遍历的结果为:0 1 3 7 4 2 5 6

中序遍历的结果为:7 3 1 4 0 5 2 6

后序遍历的结果为:7 3 4 1 5 6 2 0

计算深度

计算深度-递归，依次计算其左右子树的深度，选其大者

 public static int deep(Node node) {
    if (node !=null){
      int leftDeep= 1, rightDeep=1;
      if (node.getLeftNode()!=null)
          leftDeep=leftDeep+deep(node.getLeftNode());

     if (node.getRightNode() !=null)
        rightDeep=rightDeep+deep(node.getRightNode());

      return Math.max(leftDeep, rightDeep);

    }
}

插入

   public Node insert(Node root, int key){

        Node newNode =new Node(key，null,null);

        Node current = root;

        Node parent = null;

        
        if (current == null){ 
            root = newNode;
            return newNode;
        }

        while (true)
        {
            parent = current;

            if (key < current.getData()){

                current = current.getLeftNode();

                if (current == null)

                {               
                    parent.setLeftNode(newNode);

                    return newNode;

                }

            }else {

                current = current.getRighNode();

                if (current ==null){

                    parent.setRighNode( newNode);

                    return newNode;

                }

            }

        }

    }