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();
            TreeNode root = creatTree(str);
            inOrder(root);
        }
    }

    public static int i = 0;

    private static TreeNode creatTree(String str) {
        TreeNode root = null;
        char ch = str.charAt(i);
        if (ch != '#') {
            root = new TreeNode(ch);
            i++;
            root.left = creatTree(str);
            root.right = creatTree(str);
        }
        else {
            i++;
        }
        return root;
    }

    private static void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }
}