题解 | 二叉树遍历

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    static class BTNode {
        public char val;
        public BTNode left;
        public BTNode right;
        public BTNode(char val){
            this.val=val;
        }
    }
    public int i = 0;
    public BTNode create(String str) {
        if(str.charAt(i)=='#'||i>=str.length()){
            i++;
            return null;
        }
        BTNode root = new BTNode(str.charAt(i));
        i++;
        root.left = create(str);
        root.right = create(str);
        return root;
    }
    public void inOrder(BTNode root) {
        if (root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }
    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();
            Main ma = new Main();
            BTNode root = ma.create(str);
            ma.inOrder(root);
        }
    }

}