CS 201: Data Structures (Winter 2017)

Recursive Queue Hint

To represent a completely empty queue:

• front = null
• middle = null
• back = null

To represent a queue that has one element:

• front = element
• middle = null
• back = null

To represent a queue that has two elements:

• front = element
• middle = null
• back = element

To represent a queue that three or more elements:

• front = element
• middle = another (recursive) queue
• back = element

Note that middle should never refer to a queue that is empty. If the queue that middle points to becomes empty, then set middle to null directly.