Codec.java

/*
 * @lc app=leetcode id=297 lang=java
 *
 * [297] Serialize and Deserialize Binary Tree
 */

// @lc code=start

import java.util.LinkedList;
import java.util.Queue;

import javax.swing.tree.TreeNode;

/**
 * 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 "null";

        StringBuilder sb = new StringBuilder();
        Queue<TreeNode> q = new LinkedList<>();
        q.add(root);

        while (!q.isEmpty()) {
            TreeNode curr = q.poll();

            if (curr == null) {
                sb.append("null,");
                continue;
            }

            sb.append(curr.val).append(",");
            q.add(curr.left);
            q.add(curr.right);
        }
        return sb.toString();
    }

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

        String[] arr = data.split(",");
        TreeNode root = new TreeNode(Integer.parseInt(arr[0]));
        Queue<TreeNode> q = new LinkedList<>();
        q.add(root);
        int i = 1;

        // KEY Take away need to get more familar with leetcode TreeNode
        while (!q.isEmpty() && i < arr.length) {
            TreeNode curr = q.poll();

            if (!arr[i].equals("null")) {
                curr.left = new TreeNode(Integer.parseInt(arr[i]));
                q.add(curr.left);
            }
            i++;

            if (i < arr.length && !arr[i].equals("null")) {
                curr.right = new TreeNode(Integer.parseInt(arr[i]));
                q.add(curr.right);
            }
            i++;
        }

        return root;
    }
}

// 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));
// @lc code=end