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 "";
        }
        StringBuilder builder = new StringBuilder();
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        while (!queue.isEmpty()) {
            TreeNode node = queue.poll();
            if (node == null) {
                builder.append("#").append("_");
            } else {
                builder.append(node.val).append("_");
                queue.add(node.left);
                queue.add(node.right);
            }
        }
        return builder.toString();
    }
    TreeNode Deserialize(String str) {
        if (str.equals("")) {
            return null;
        }

        String[] split = str.split("_");
        Queue<TreeNode> queue = new LinkedList<>();
        TreeNode root = new TreeNode(Integer.parseInt(split[0]));
        queue.add(root);
        for (int i = 1; i < split.length - 1; i += 2) {
            TreeNode node = queue.poll();
            String a = split[i];
            String b = split[i + 1];
            if (!"#".equals(a)) {
                TreeNode nodeA = new TreeNode(Integer.parseInt(a));
                node.left = nodeA;
                queue.add(nodeA);
            }
            if (!"#".equals(b)) {
                TreeNode nodeB = new TreeNode(Integer.parseInt(b));
                node.right = nodeB;
                queue.add(nodeB);
            }
        }

        return root;
    }
}