import java.util.*;
class TreeNode {
  int val = 0;
  TreeNode left = null;
  TreeNode right = null;
  public TreeNode(int val) {
    this.val = val;
  }
}
public class CheckCompletion {
  public boolean checking(TreeNode root) {
    Queue<TreeNode> queue = new LinkedList<TreeNode>();
    boolean leaf = false; // 叶子结点
    TreeNode left;
    TreeNode right;
    queue.add(root);
    while (!queue.isEmpty()) {
      root = queue.poll();
      left = root.left;
      right = root.right;
      if ((leaf&&(left!=null||right!=null)) || (left==null&&right!=null)) {
        // 如果之前层遍历的结点没有右孩子，且当前的结点有左或右孩子，直接返回false
        // 如果当前结点有右孩子却没有左孩子，直接返回false
        return false;
      }
      if (left != null) {
        queue.offer(root.left);
      }
      if (right != null) {
        queue.offer(root.right);
      }else {
        leaf = false; // 如果当前结点没有右孩子，那么之后层遍历到的结点必须为叶子结点
      }
    }
    return true;
  }
}