Complete binary tree

Ideas ： Sequence traversal binary tree
If a node , Left and right children are not empty , be pop The node , Put their left and right children in line
If a node , The left child is empty , The right child is not empty , Then the tree must not be a complete binary tree
If a node , The left child is not empty , The right child is empty ; Or left and right children are empty , Then all the nodes in the queue after the node are leaf nodes ; This tree is a complete binary tree , Otherwise return to false.

    public static class Node {
    
		public int value;
		public Node left;
		public Node right;
 
		public Node(int data) {
    
			this.value = data;
		}
	}
	public static boolean isCBT(Node head) {
    
		if (head == null) {
    
			return true;
		}
		Queue<Node> queue = new LinkedList<Node>();
		boolean leaf = false;
		Node l = null;
		Node r = null;
		queue.offer(head);
		while (!queue.isEmpty()) {
    
			head = queue.poll();
			l = head.left;
			r = head.right;
			if ((leaf && (l != null || r != null)) || (l == null && r != null)) {
    
				return false;// The current node is not a leaf node and the previous node has a leaf node  ||  The current node has right children but no left children 
			}
			if (l != null) {
    
				queue.offer(l);
			}
			if (r != null) {
    
				queue.offer(r);
			} else {
    
				leaf = true;// No child is a leaf node 
			}
		}
		return true;
	}

Refer to the boss's