Min Stack Problem Statement

Design a special stack that supports the following operations in constant time:

1. Push(num): Insert the given number into the stack.
2. Pop: Remove and return the top element from the stack; return -1 if the stack is empty.
3. Top: Return the top element of the stack; return -1 if the stack is empty.
4. getMin: Return the minimum element in the stack; return -1 if the stack is empty.

Example:

Input:

1
5
1 1
1 2
4
2
3

Output:

1 2 1

Explanation:

Initially, the stack is empty.
1. Push 1: Stack becomes [1].
2. Push 2: Stack becomes [2, 1].
3. getMin: Minimum is 1.
4. Pop: Topmost is 2, stack becomes [1].
5. Top: Topmost is 1.

Constraints:

• 1 ≤ T ≤ 1000
• 1 ≤ N ≤ 100000
• ΣN ≤ 200000
• 1 ≤ X ≤ 109