创建二叉树

package binaryTree;
import java.util.*;

//定义二叉树的结点
class TreeNode {
    
    int val;
    TreeNode left;
    TreeNode right;

    public TreeNode(){
    

    }

    public TreeNode(int val){
    
        this.val = val;
    }
    public TreeNode(int val, TreeNode left, TreeNode right){
    
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

public class CreatTree {
    
    public static void main(String[] args) {
    
        System.out.println("输入树的节点值(输入-1则终止)：");
        Scanner sc = new Scanner(System.in);
        LinkedList<Integer> list = new LinkedList<>();
        while(true){
    
            int temp = sc.nextInt();
            if(temp == -1){
    
                break;
            }else{
    
                list.addLast(temp);
            }
        }
        TreeNode root = create(list);
        List<Integer> tree = traverse(root);
        System.out.print("中序遍历结果:");
        System.out.println(tree);
    }

    //（按先序递归）创建二叉树
    public static TreeNode create(LinkedList<Integer> list){
    
        if(list==null||list.size()==0){
    
            return null;
        }
        TreeNode node = null;
        int data = list.removeFirst();
        if(data!=0){
    
            node = new TreeNode(data);
            node.left = create(list);
            node.right = create(list);
        }
        return node;
    }

    //非递归中序遍历
    public static List<Integer> traverse(TreeNode root){
    
        List<Integer> list = new ArrayList<>();
        if(root == null){
    
            return list;
        }
        Deque<TreeNode> stack = new LinkedList<>();
        TreeNode cur = root;
        while(cur!=null||!stack.isEmpty()){
    
            if(cur!=null){
    
                stack.push(cur);
                cur = cur.left;
            }else{
    
                cur = stack.pop();
                list.add(cur.val);
                cur = cur.right;
            }
        }
        return list;
    }
}

测试案例：