Min Stack

Version #1 Always push to the minStack
public class MinStack {
    private Stack<Integer> minStack;
    private Stack<Integer> stack;
    public MinStack() {
        // do initialize if necessary
        minStack = new Stack<>();
        stack = new Stack<>();
    }

    public void push(int number) {
        // write your code here
        if (minStack.isEmpty()) {
            minStack.push(number);
        } else {
            minStack.push(Math.min(number, minStack.peek()));
        }
        stack.push(number);
    }

    public int pop() {
        // write your code here
        minStack.pop();
        return stack.pop();
    }

    public int min() {
        // write your code here
        return minStack.peek();
    }
}