题目链接

297. 二叉树的序列化与反序列化

思路

代码

class Codec {
    // Encodes a tree to a single string.
    public String serialize(TreeNode root) {
        if(root == null){
            return "";
        }

        StringBuilder sb = new StringBuilder();
        Queue<TreeNode> queue = new LinkedList<>();

        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode node = queue.poll();

            if(node == null){
                sb.append("X,");
            }else{
                sb.append(node.val + ",");
                queue.offer(node.left);
                queue.offer(node.right);
            }
        }

        return sb.toString();
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        if(Objects.equals(data, "")){
            return null;
        }

        Queue<String> nodes = new ArrayDeque<>(Arrays.asList(data.split(",")));
        TreeNode root = new TreeNode(Integer.parseInt(nodes.poll()));
        Queue<TreeNode> queue = new ArrayDeque<>();

        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode node = queue.poll();
            String left = nodes.poll();
            String right = nodes.poll();

            if(!left.equals("X")){
                node.left = new TreeNode(Integer.parseInt(left));
                queue.add(node.left);
            }
            if(!right.equals("X")){
                node.right = new TreeNode(Integer.parseInt(right));
                queue.add(node.right);
            }
        }

        return root;
    }
}