add some test in c/. about 'const' in '#include', and `struct`'s
syntax.
RBTree: For the InsertFix part. I waste a lot of time in
discussing LL/LR/RL/RR. That is correct, but now I found that
Sibling(N->parent) is always RED if the sibling is not leaf!!!
That means I can just set N->parent's and its sibling's color
to BLACK, and then all adjustment would be done...
It seems like Insertion has finished
Insertion is OK. But deletion is wrong, since all leaves are point
to the same node. I will change the implementation, let leaves are
different.
What I have done is a permature optimization!
Insert complete. Leaf node is not shared
Red-black tree finished
add AVL tree. BST insert complete.
AVL insert complete
fix insert LR/RL bugs
AVL delete operation finished