层序遍历代码

public void level(Node head){
	if(head == null){
		return;
	}

	Queue<Node> queue = new LinkedList<>();
	queue.add(head);

	while(!queue.isEmpty()){

		Node curr = queue.poll();
		System.out.println(curr.value);

		if(curr.left != null){
			queue.add(curr.left);
		}
		if(curr.right != null){
			queue.add(curr.right);
		}
	}
}

前序遍历序列化与反序列化

public class SerializeDemo{

	//序列化
	public static Queue<String> preSerial(Node head) {
		Queue<String> ans = new LinkedList<>();
		pres(head, ans);
		return ans;
	}

	public static void pres(Node head, Queue<String> ans) {
		if (head == null) {
			ans.add(null);
		} else {
			ans.add(String.valueOf(head.value));
			pres(head.left, ans);
			pres(head.right, ans);
		}
	}

	//反序列化
	public static Node buildByPreQueue(Queue<String> prelist) {
		if (prelist == null || prelist.size() == 0) {
			return null;
		}
		return preb(prelist);
	}

	public static Node preb(Queue<String> prelist) {
		String value = prelist.poll();
		if (value == null) {
			return null;
		}
		Node head = new Node(Integer.valueOf(value));
		head.left = preb(prelist);
		head.right = preb(prelist);
		return head;
	}

}

层序遍历序列化与反序列化

public class SerializeDemo2{

	public static Queue<String> levelSerial(Node head) {
		Queue<String> ans = new LinkedList<>();
		if (head == null) {
			ans.add(null);
		} else {
			ans.add(String.valueOf(head.value));
			Queue<Node> queue = new LinkedList<Node>();
			queue.add(head);
			while (!queue.isEmpty()) {
				head = queue.poll(); // head 父   子
				if (head.left != null) {
					ans.add(String.valueOf(head.left.value));
					queue.add(head.left);
				} else {
					ans.add(null);
				}
				if (head.right != null) {
					ans.add(String.valueOf(head.right.value));
					queue.add(head.right);
				} else {
					ans.add(null);
				}
			}
		}
		return ans;
	}

	public static Node buildByLevelQueue(Queue<String> levelList) {
		if (levelList == null || levelList.size() == 0) {
			return null;
		}
		Node head = generateNode(levelList.poll());
		Queue<Node> queue = new LinkedList<Node>();
		if (head != null) {
			queue.add(head);
		}
		Node node = null;
		while (!queue.isEmpty()) {
			node = queue.poll();
			node.left = generateNode(levelList.poll());
			node.right = generateNode(levelList.poll());
			if (node.left != null) {
				queue.add(node.left);
			}
			if (node.right != null) {
				queue.add(node.right);
			}
		}
		return head;
	}

	public static Node generateNode(String val) {
		if (val == null) {
			return null;
		}
		return new Node(Integer.valueOf(val));
	}
}