剑指 Offer 30. 包含min函数的栈（单调栈）

剑指 Offer 30. 包含min函数的栈

class MinStack {

    

    Deque st = new ArrayDeque(), min = new ArrayDeque(); 


    public MinStack() {

    }
    
    public void push(int x) {
        st.push(x);
        if(min.isEmpty()|| min.peek() >= x) {
            min.push(x);
        }
    }
    
    public void pop() {
        int x = st.pop();
        if(x == min.peek()) {
            min.pop();
        }
    }
    
    public int top() {
        return st.peek();
    }
    
    public int min() {
        return min.peek();
    }
}