What is the purpose of a count variable in a linked list?

• A. To store data values
• B. To keep track of the number of nodes in the list
• C. To size the array backing storage
• D. To track the maximum node value

Answer: (B)

The count variable is a running tally of how many nodes are currently in the list. This lets you know the list’s size in constant time, without traversing from head to tail every time you need to query length. It also makes emptiness checks and size-dependent operations straightforward and reliable during insertions or deletions, since you simply increment or decrement the count as the list changes. It’s not used to store the data values themselves (those live in the nodes) and it doesn’t relate to any array backing storage or to a maximum node value. The important idea is that the count provides quick, accurate size information by keeping an up-to-date tally of nodes.