题解 | #二叉树遍历#

import java.util.Scanner;

class TreeNode{
    public char val;
    public TreeNode left;
    public TreeNode right;
    public TreeNode(char val){
        this.val = val;
    }
}
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
           String str = in.nextLine();
           //创建二叉树
           TreeNode root = createTree(str);
           //进行中序遍历
           inOrder(root);
        }
    }
    public static int i = 0;
    public static TreeNode createTree(String str){
        TreeNode root = null;
        if(str.charAt(i) != '#'){
            root = new TreeNode(str.charAt(i));//创建根节点
            i++;
		  //递归创建左右子节点
            root.left = createTree(str);
            root.right = createTree(str);
        }else{
            i++;
        }
        return root;
    }
    public static void inOrder(TreeNode root){
        if(root == null)return;
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }
}