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Min Stack
MediumData StructuresDescription
Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
Implement the `MinStack` class:
- `push(val)` pushes the element val onto the stack.
- `pop()` removes the element on the top of the stack.
- `top()` gets the top element of the stack.
- `getMin()` retrieves the minimum element in the stack.
You must implement a solution with O(1) time complexity for each function.
**Note:** For this problem, implement operations as a function that takes a list of commands and returns the results. Return `null` for void operations (push, pop).
Example 1
Input: operations = [["push",-2],["push",0],["push",-3],["getMin"],["pop"],["top"],["getMin"]]
Output: [null,null,null,-3,null,0,-2]
Explanation: push(-2), push(0), push(-3), getMin() returns -3, pop() removes -3, top() returns 0, getMin() returns -2.
Constraints
- -2^31 <= val <= 2^31 - 1
- Methods pop, top and getMin operations will always be called on non-empty stacks.
- At most 3 * 10^4 calls will be made to push, pop, top, and getMin.
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