Package g1601_1700.s1670_design_front_middle_back_queue

Class FrontMiddleBackQueue

java.lang.Object
g1601_1700.s1670_design_front_middle_back_queue.FrontMiddleBackQueue
public class FrontMiddleBackQueue extends Object
1670 - Design Front Middle Back Queue\. Medium 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:** **Input:** ["FrontMiddleBackQueue", "pushFront", "pushBack", "pushMiddle", "pushMiddle", "popFront", "popMiddle", "popMiddle", "popBack", "popFront"] [ [], [1], [2], [3], [4], [], [], [], [], []] **Output:** [null, null, null, null, null, 1, 3, 4, 2, -1] **Explanation:** FrontMiddleBackQueue q = new FrontMiddleBackQueue(); q.pushFront(1); // [1] q.pushBack(2); // [1, 2] q.pushMiddle(3); // [1, 3, 2] q.pushMiddle(4); // [1, 4, 3, 2] q.popFront(); // return 1 -> [4, 3, 2] q.popMiddle(); // return 3 -> [4, 2] q.popMiddle(); // return 4 -> [2] q.popBack(); // return 2 -> [] q.popFront(); // return -1 -> [] (The queue is empty) **Constraints:** * 1 <= val <= 109 * At most `1000` calls will be made to `pushFront`, `pushMiddle`, `pushBack`, `popFront`, `popMiddle`, and `popBack`.

  • Constructor Details

    • FrontMiddleBackQueue

      public FrontMiddleBackQueue()

  • Method Details

    • pushFront

      public void pushFront(int val)

    • pushMiddle

      public void pushMiddle(int val)

    • pushBack

      public void pushBack(int val)

    • popFront

      public int popFront()

    • popMiddle

      public int popMiddle()

    • popBack

      public int popBack()