刷题记录-剑指offer37：序列化二叉树

请实现两个函数，分别用来序列化和反序列化二叉树。

https://leetcode-cn.com/problems/xu-lie-hua-er-cha-shu-lcof/

注意：序列化是一定非要得到和示例一样的结果："[1,2,3,null,null,4,5]"，可以是"[1,2,3,null,null,4,5,null,null,null,null]"，这样的话就是一个二叉树的bfs，比较简单。因为题目里写了

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));

只要不影响反序列化的结果就行。

public class Codec {
    public String serialize(TreeNode root) {
        if(root == null) return "[]";
        StringBuilder res = new StringBuilder("[");
        Queue<TreeNode> queue = new LinkedList<>() {{ add(root); }};
        while(!queue.isEmpty()) {
            TreeNode node = queue.poll();
            if(node != null) {
                res.append(node.val + ",");
                queue.add(node.left);
                queue.add(node.right);
            }
            else res.append("null,");
        }
        res.deleteCharAt(res.length() - 1);
        res.append("]");
        return res.toString();
    }

    public TreeNode deserialize(String data) {
        if(data.equals("[]")) return null;
        String[] vals = data.substring(1, data.length() - 1).split(",");
        TreeNode root = new TreeNode(Integer.parseInt(vals[0]));
        Queue<TreeNode> queue = new LinkedList<>() {{ add(root); }};
        int i = 1;
        while(!queue.isEmpty()) {
            TreeNode node = queue.poll();
            if(!vals[i].equals("null")) {
                node.left = new TreeNode(Integer.parseInt(vals[i]));
                queue.add(node.left);
            }
            i++;
            if(!vals[i].equals("null")) {
                node.right = new TreeNode(Integer.parseInt(vals[i]));
                queue.add(node.right);
            }
            i++;
        }
        return root;
    }
}