Create a binary tree
root = Node ( 15 ) NEW_LINE root . left = Node ( 10 ) NEW_LINE root . right = Node ( 20 ) NEW_LINE root . left . left = Node ( 8 ) NEW_LINE root . left . right = Node ( 12 ) NEW_LINE root . right . left = Node ( 16 ) NEW_LINE root . right . right = Node ( 25 ) NEW_LINE