【设计数据结构】面试官：请设计一个「最小栈」...

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

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

解释：
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin();   --> 返回 -3.
minStack.pop();
minStack.top();      --> 返回 0.
minStack.getMin();   --> 返回 -2.

class MinStack {
    Deque<Integer> data = new ArrayDeque<>();
    Deque<Integer> help = new ArrayDeque<>();

    public void push(int val) {
        data.addLast(val);
        if (help.isEmpty() || help.peekLast() >= val) {
            help.addLast(val);
        } else {
            help.addLast(help.peekLast());
        }
    }
    
    public void pop() {
        data.pollLast();
        help.pollLast();
    }
    
    public int top() {
        return data.peekLast();
    }
    
    public int getMin() {
        return help.peekLast();
    }
}