155.最小栈

`

class MinStack{
    Deque<Integer> stack;
    Deque<Integer> minStack;
    int min = Integer.MAX_VALUE;
    public MinStack() {
        stack = new ArrayDeque<>();
        minStack = new ArrayDeque<>();
    }

    public void push(int val) {
        stack.push(val);
        if(val<min){
            minStack.push(val);
            min = val;
        }else{
            minStack.push(min);
        }
    }

    public void pop() {
        stack.pop();
        minStack.pop();
        if(minStack.isEmpty()){
            min = Integer.MAX_VALUE;
            return;
        }
        min = minStack.peek();
    }

    public int top() {
        return stack.peek();
    }

    public int getMin() {
        return min;
    }
}`