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 "";
        }
        Queue<TreeNode> queue = new LinkedList<>();
        TreeNode cur = root;
        queue.offer(cur);
        StringBuilder sb = new StringBuilder();
        while (!queue.isEmpty()) {
            cur = queue.poll();
            sb.append(cur.val + "_");
            if (cur.val != -1) {
                queue.offer(cur.left != null ? cur.left : new TreeNode(-1));
                queue.offer(cur.right != null ? cur.right : new TreeNode(-1));
            }
        }
        return sb.toString();
    }

    TreeNode Deserialize(String str) {
        if (str == null || str.length() < 1) {
            return null;
        }
        String[] parts = str.split("_");
        Queue<TreeNode> queue = new LinkedList<>();
        TreeNode root = new TreeNode(Integer.parseInt(parts[0]));
        queue.offer(root);
        for (int i = 1; i < parts.length - 1; i += 2) {
            TreeNode cur = queue.poll();
            int left = Integer.parseInt(parts[i]);
            int right = Integer.parseInt(parts[i + 1]);
            if (left != -1) {
                cur.left = new TreeNode(left);
                queue.offer(cur.left);
            }
            if (right != -1) {
                cur.right = new TreeNode(right);
                queue.offer(cur.right);
            }
        }
        return root;
    }








}