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) {
        if (root == null)
            return "{}"; //为空返回{}
        StringJoiner sj = new StringJoiner(",", "{", "}");
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        while (!queue.isEmpty()) {
            TreeNode node = queue.poll();
            sj.add(node == null ? "#" : String.valueOf(node.val));
            if (node != null) {
                queue.add(node.left);
                queue.add(node.right);
            }
        }
        String res = sj.toString();
        while (res.endsWith("#}")) {
            res = res.substring(0, res.length() - 3) + "}";
        }
        return res;
    }

    TreeNode Deserialize(String str) {
        if (str.equals("{}")) return null;
        String[] strs = str.substring(1, str.length() - 1).split(",");
        Queue<TreeNode> queue = new LinkedList<>();
        int i = 0;
        TreeNode root = new TreeNode(Integer.parseInt(strs[i++]));
        queue.add(root);
        while (!queue.isEmpty() && i < strs.length) {
            TreeNode node = queue.poll();
            if (node == null) continue;
            TreeNode leftNode = strs[i].equals("#") ? null : new TreeNode(Integer.parseInt(
                                    strs[i]));
            i++;
            node.left = leftNode;
            queue.add(leftNode);
            if (i >= strs.length) break;
            TreeNode rightNode = strs[i].equals("#") ? null : new TreeNode(Integer.parseInt(
                                     strs[i]));
            i++;
            node.right = rightNode;
            queue.add(rightNode);
        }
        return root;
    }
}