create a binary tree
root = getnode ( 20 ) NEW_LINE root . left = getnode ( 10 ) NEW_LINE root . right = getnode ( 30 ) NEW_LINE root . left . left = getnode ( 5 ) NEW_LINE root . left . right = getnode ( 15 ) NEW_LINE root . left . right . left = getnode ( 12 ) NEW_LINE root . right . left = getnode ( 25 ) NEW_LINE root . right . right = getnode ( 40 ) NEW_LINE