题解 | #序列化二叉树#

import java.util.*;
/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }


}
*/
public class Solution {
    String Serialize(TreeNode root) {
        StringBuilder sb = new StringBuilder();
        dfs1(root, sb);
        return sb.toString();
    }


    TreeNode Deserialize(String str) {
        String[] arr = str.split(",");
        LinkedList<String> queue = new LinkedList<>();
        for(String st:arr){
            queue.offer(st);
        }
        TreeNode node= dfs2(queue);
        return node;
    }



    public void dfs1(TreeNode node, StringBuilder sb) {
        //先序遍历
        if (node == null) {
            //遍历到空
            sb.append("null").append(",");
            return;
        }
        sb.append(node.val).append(",");
        dfs1(node.left, sb);
        dfs1(node.right, sb);
    }

    public TreeNode dfs2(LinkedList<String> queue){
            if(queue.isEmpty()){
                return null;
            }
            String s=queue.poll();
            if(s.equals("null")){
                return null;
            }
            TreeNode node=new TreeNode(Integer.parseInt(s));
            node.left=dfs2(queue);
            node.right=dfs2(queue);
            return node;
    }
















}