Min Stack

1. Title

Min Stack

2. Http address

https://leetcode.com/problems/min-stack/

3. The question

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.

4 My code(AC)

 1 public class MinStack {
 2 
 3     // Accepted 
 4     public LinkedList<Integer> stack = new LinkedList<Integer>();
 5     public LinkedList<Integer> min_stack = new LinkedList<Integer>();
 6     
 7       public void push(int x) {
 8           
 9               stack.offerFirst(x);
10               
11               if ( min_stack.isEmpty() || x < min_stack.peekFirst()) {
12                   min_stack.offerFirst(x);
13               }else{
14                   min_stack.offerFirst(min_stack.peekFirst());
15               }
16       }
17 
18      public void pop() {
19             stack.pollFirst();
20             min_stack.pollFirst();
21      }
22 
23         public int top() {
24             return stack.peekFirst();
25         }
26 
27         public int getMin() {
28                 return min_stack.peekFirst();
29         }
30 }