Min Stack in Java: Explanation & Practice

Design stack that supports getMin in O(1)

Problem summary

Design a stack that supports push, pop, top, and retrieving minimum element in constant time.

Starter code

public class Main {
    public static void main(String[] args) {
        // Implement MinStack
        // push(-2), push(0), push(-3)
        // getMin() → -3
        // pop()
        // top() → 0
        // getMin() → -2
        // Print operations in order
    }
}

Expected output and test cases

push -2,0,-3; getMin; pop; top; getMin
```
Min: -3
Top: 0
Min: -2
```
push -2,0,-1; getMin twice
```
Min: -2
Min: -2
```
push 1; getMin
```
Min: 1
```

Hints

Use two stacks: one for values, one for minimums
When pushing, also push to min stack if <= current min
When popping, also pop from min stack if value equals current min
Alternative: store pairs of (value, minSoFar)

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