难度困难
请实现两个函数，分别用来序列化和反序列化二叉树。
示例:
你可以将以下二叉树：
1
/ \
2 3
/ \
4 5
序列化为 "[1,2,3,null,null,4,5]"
注意：本题与主站 297 题相同：https://leetcode-cn.com/problems/serialize-and-deserialize-binary-tree/
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Codec {
// Encodes a tree to a single string.
public String serialize(TreeNode root) {
if (root == null) {
return "[]";
}
StringBuilder sb = new StringBuilder();
sb.append("[");
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
while (!queue.isEmpty()) {
TreeNode treeNode = queue.poll();
if (treeNode == null) {
sb.append("null,");
} else {
sb.append(treeNode.val).append(",");
queue.add(treeNode.left);
queue.add(treeNode.right);
}
}
sb.deleteCharAt(sb.length() - 1);
sb.append("]");
return sb.toString();
}
// Decodes your encoded data to tree.
public TreeNode deserialize(String data) {
if (data == "[]") {
return null;
}
String[] strings = data.substring(1, data.length() - 1).split(",");
TreeNode root = new TreeNode(Integer.parseInt(strings[0]));
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
int i = 1;
while (!queue.isEmpty()) {
TreeNode treeNode = queue.poll();
if (!strings[i].equals("null")) {
treeNode.left = new TreeNode(Integer.parseInt(strings[i]));
queue.add(treeNode.left);
}
i++;
if (!strings[i].equals("null")) {
treeNode.right = new TreeNode(Integer.parseInt(strings[i]));
queue.add(treeNode.right);
}
i++;
}
return root;
}
}
// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));