Solution: Min Stack

Statement

Design a custom stack, Min Stack, allowing us to push, pop, and retrieve the minimum value in constant time. Implement the following methods for Min Stack struct:

• NewMinStack(): This initializes the Min Stack object.

• Pop(): This removes and returns from the stack the value that was most recently pushed onto it.

• Push(): This pushes the provided value onto the stack.

• Min Number(): This returns the minimum value in the stack in $O(1)$ time.

Note: The time complexity of all the methods above should be $O(1)$.

Constraints:

• $-10^{4} \leq$ value $\leq 10^{4}$

• The Pop() and Min Number() methods will always be called on non-empty stacks.

• At most, $10^3$ calls will be made to Push(), Pop(), and Min Number().