Implement a stack data structure with the following operations:

• push(val): Push an element onto the stack
• pop(): Remove and return the top element from the stack
• top(): Return the top element without removing it
• empty(): Return whether the stack is empty

You can choose to implement the stack using either:

1. Linked List - Each node points to the next node
2. Circular Array - Fixed-size array with wrapping

Examples

Example 1

Input:  ["Stack", "push", "push", "top", "pop", "empty"]

[[], [1], [2], [], [], []] Output: [null, null, null, 2, 2, false]

Example 2

Input:  ["Stack", "push", "pop", "empty"]

[[], [10], [], []] Output: [null, null, 10, true]

Constraints

• 1 <= val <= 10^9
• At most 10^4 calls will be made to each function
• pop and top will only be called on non-empty stacks

How the tests work: each test is a sequence of calls. operations[i] is the method called with arguments[i]; the first entry constructs the class. The expected output lists what every call returns — null for the constructor and for methods that return nothing.