牛客KY11—二叉树的遍历

题目要求：

思路：创建一个树，通过Scanner获取字符串，使用Index来记录字符串的下标，每次++，如果为#则不放入树中，递归实现前序遍历，然后递归实现中序遍历即可

import java.util.*;
public class Main {
 
    public static class TreeNode {
        public char val;
        public TreeNode left;
        public TreeNode right;
        
        public TreeNode(char val){
            this.val = val;
        }
    }
     
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        while(scan.hasNextLine()){
            String s = scan.nextLine();//接收scan获取的字符
             TreeNode root = create(s);
            InOrder(root);
        }
     }   
    
    public static void InOrder(TreeNode root){
        if(root == null){
            return;
        }        
        InOrder(root.left);
        System.out.print(root.val+" ");
        InOrder(root.right);
    }
    
    static int Index = 0;
    
    public static TreeNode create(String s){
        TreeNode root = null;
        if(s.charAt(Index) != '#'){
            root = new TreeNode(s.charAt(Index));
            Index++;//每次++获取到下一个字符
            root.left = create(s);
            root.right = create(s);
        }else{
            Index++;
        }
        return root;
    }
}