```
public class MinStack
extends Object
```
155 - Min Stack\. Easy Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. Implement the `MinStack` class: * `MinStack()` initializes the stack object. * `void push(int val)` pushes the element `val` onto the stack. * `void pop()` removes the element on the top of the stack. * `int top()` gets the top element of the stack. * `int getMin()` retrieves the minimum element in the stack. **Example 1:** **Input** ["MinStack","push","push","push","getMin","pop","top","getMin"] [ [],[-2],[0],[-3],[],[],[],[]] **Output:** [null,null,null,null,-3,null,0,-2] **Explanation:** MinStack minStack = new MinStack(); minStack.push(-2); minStack.push(0); minStack.push(-3); minStack.getMin(); // return -3 minStack.pop(); minStack.top(); // return 0 minStack.getMin(); // return -2 **Constraints:** * -2³¹ <= val <= 2³¹ - 1 * Methods `pop`, `top` and `getMin` operations will always be called on **non-empty** stacks. * At most 3 * 10⁴ calls will be made to `push`, `pop`, `top`, and `getMin`.

Class MinStack