Design Front Middle Back Queue
medium · 57% accepted · 816 likes · top 52%
array · linked list · design · queue · doubly-linked list · data stream
Description
Design a queue that supports push and pop operations in the front, middle, and back.
Implement the FrontMiddleBack class:
- FrontMiddleBack() Initializes the queue.
- void pushFront(int val) Adds val to the front of the queue.
- void pushMiddle(int val) Adds val to the middle of the queue.
- void pushBack(int val) Adds val to the back of the queue.
- int popFront() Removes the front element of the queue and returns it. If the queue is empty, return -1.
- int popMiddle() Removes the middle element of the queue and returns it. If the queue is empty, return -1.
- int popBack() Removes the back element of the queue and returns it. If the queue is empty, return -1.
Notice that when there are two middle position choices, the operation is performed on the frontmost middle position choice. For example:
- Pushing 6 into the middle of [1, 2, 3, 4, 5] results in [1, 2, 6, 3, 4, 5].
- Popping the middle from [1, 2, 3, 4, 5, 6] returns 3 and results in [1, 2, 4, 5, 6].
Example 1:
Example 2:
Solution