List

* Single Linked List
- One Head Pointer Must Be Associated
To change the head pointer in one sub-routine, the pointer itself instead of its copy must be changed. Therefore the pointer to head pointer must be passed in ANY sub-routines which changes the head/tail pointers.
- Lists End With NULL
This must be checked when the traverse happens.
- Insert And Delete
When deleting one element in the list, the element before this one must be obtained.
When inserting one element, it depends on whether it is inserted before or after a specific element.
- Free Every Element in The List
- Special Cases Processing: Head and Tail; Length of List == 0, 1, 2, ...

* Examples
- Implement stack data structure
We could implement stack with variable array or single linked list. Due to the heavy overhead of maintaining the memory of elements, variable array might be suitable for small data set.
- Insert and delete function in list with head and tail pointers
How to process special cases?
- Get the mth element in reverse order in one list
1) n = N - m; Two traverses to get N and n; O(N)
2) Two pointers with the distance of m
- How to check if the list contains loop?
Fast and slow pointers
- How to delete one element if only the pointer to this element is given, i.e. without traversing?
Copy the content of next element to this one and delete next element.
- How to reverse one list with/without recursion?