import sys
def levelOrder(root):
    if root is None:
        return
    q = [root]
    while(len(q) > 0):
        sys.stdout.write(str(q[0].data) + ' ')
        n = q.pop(0)
        if not n.left is None:
            q.append(n.left)
        if not n.right is None:
            q.append(n.right)