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)

•  

  public class MinStack {
  
      // Accepted 
      public LinkedList<Integer> stack = new LinkedList<Integer>();
      public LinkedList<Integer> min_stack = new LinkedList<Integer>();
      
        public void push(int x) {
            
                stack.offerFirst(x);
                
                if ( min_stack.isEmpty() || x < min_stack.peekFirst()) {
                    min_stack.offerFirst(x);
                }else{
                    min_stack.offerFirst(min_stack.peekFirst());
                }
        }
  
       public void pop() {
              stack.pollFirst();
              min_stack.pollFirst();
       }
  
          public int top() {
              return stack.peekFirst();
          }
  
          public int getMin() {
                  return min_stack.peekFirst();
          }
  }