Min Stack

1. Title

Min Stack

2. Http address

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

 1 import java.util.*;
 2 public class MinStack {
 3 
 4     // Accepted 
 5     public LinkedList<Integer> stack = new LinkedList<Integer>();
 6     public LinkedList<Integer> min_stack = new LinkedList<Integer>();
 7     
 8       public void push(int x) {
 9           
10               stack.offerFirst(x);
11               
12               if ( min_stack.isEmpty() || x < min_stack.peekFirst()) {
13                   min_stack.offerFirst(x);
14               }else{
15                   min_stack.offerFirst(min_stack.peekFirst());
16               }
17       }
18 
19      public void pop() {
20             stack.pollFirst();
21             min_stack.pollFirst();
22      }
23 
24         public int top() {
25             return stack.peekFirst();
26         }
27 
28         public int getMin() {
29                 return min_stack.peekFirst();
30         }
31 }

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)