Design a stack that supports `push`, `pop`, and `getMin` in O(1). Implement `MinStack` as a class/constructor. Variant **#30**. For this problem, return the results of each operation in order.
Example 1
Input: operations (see test cases)
Output: [null, null, null, -2, null, 0]
Constraints
Acceptance: 61% · Topics: design, stack