7.[15] Suppose we have 12 integers: 60, 40, 25, 10, 50, 80, 15, 65, 30, 90, 20, 55. Construct a binary
search tree by inserting the integers, starting from 60, one after another. Please answer the following
questions for the binary search tree:
【題組】7.4 [3] What is the right child of the node containing 55?