Min Stack

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

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• getMin() -- Retrieve the minimum element in the stack.

这题相当无聊。

class MinStack {
    LinkedList<Integer> stack = new LinkedList<Integer>();
    LinkedList<Integer> minimum = new LinkedList<Integer>();
    
    public void push(int x) {
        stack.push(x);
        if(minimum.size() > 0) minimum.push(minimum.peek() > x ? x : minimum.peek());
        else minimum.push(x);
    }

    public void pop() {
        stack.pop();
        minimum.pop();
    }

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

    public int getMin() {
        return minimum.peek();
    }
}