If given node ' s ▁ left ' s right is pointing to given node and its right ' s ▁ left ▁ is ▁ pointing ▁ to ▁ the ▁ node ▁ ▁ itself ▁ then ▁ it ' s a leaf
return ( node . left != null && node . left . right == node && node . right != null && node . right . left == node ) ; }