297. 二叉树的序列化与反序列化 (JAVA)

/**
 * 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) {
        TreeNode current;
        String result = "";
        Stack<TreeNode> stack = new Stack<>();
        if(root != null) {
            stack.push(root);
        }
        while(!stack.empty()) {
            current = stack.peek();
            stack.pop();
            if(current != null) {
                stack.push(current.right);
                stack.push(current.left);
                result += current.val + ",";
            } else {
                result += "#,";
            }
        }
        return result;
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        if(data == null || data.length() == 0) return null;

        values = data.split(",");
        depth = 0;
        return deserializeDFS(data);
    }

    private TreeNode deserializeDFS(String data) {
        if(values[depth].equals("#")) {
            depth++;
            return null;
        }

        TreeNode root = new TreeNode(Integer.parseInt(values[depth]));
        depth++;
        root.left = deserializeDFS(data);
        root.right = deserializeDFS(data);

        return root;
    }

    private String[] values;
    private int depth;

}

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