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。

 1 class MinStack {

 2     LinkedList<Integer> stack = new LinkedList<Integer>();

 3     LinkedList<Integer> minimum = new LinkedList<Integer>();

 4     

 5     public void push(int x) {

 6         stack.push(x);

 7         if(minimum.size() > 0) minimum.push(minimum.peek() > x ? x : minimum.peek());

 8         else minimum.push(x);

 9     }

10 

11     public void pop() {

12         stack.pop();

13         minimum.pop();

14     }

15 

16     public int top() {

17         return stack.peek();

18     }

19 

20     public int getMin() {

21         return minimum.peek();

22     }

23 }