dsa · medium

Min Stack

GreyOrangeStackDesign

Implement a stack that also returns the current minimum in O(1).

Methods

• push(val) push onto the stack
• pop() remove the top (never called on empty)
• top() the top value (never called on empty)
• getMin() the smallest value still in the stack, not a pop

Fill in the MinStack class. The starter already walks ops / args and calls your methods — leave the driver at the bottom as-is. Constructors contribute null; booleans print as true / false.

**Example**

`` MinStack() → null push(-2) → null push(0) → null push(-3) → null getMin() → -3 pop() → null top() → 0 getMin() → -2 ``

Constraints

Calls <= 3 * 10^4

Examples

Example 1

Input:
["MinStack","push","push","push","getMin","pop","top","getMin"]
[[],[-2],[0],[-3],[],[],[],[]]

Expected:
[null,null,null,null,-3,null,0,-2]

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