Min Stack

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.

 class MinStack {
         List<Integer> stack = new ArrayList<Integer>();
     int top = -1;
     int min = Integer.MAX_VALUE;

     public void push(int x) {
         top++;
         stack.add(x);
         if(min > x){
             min = x;

         }

     }

     public void pop() {

         int element = stack.remove(top--);
         if(element == min)
         {
                 updateMin();            

         }
     }

     public int top() {
         int result = stack.get(top);

         return result;
     }

     public int getMin() {

         return this.min;
     }
     public void updateMin(){
         if(top == -1)
         {
             min = Integer.MAX_VALUE;
             return;
         }
         min = stack.get(0);
         for(int i = 1; i <= top; i++){
             if(min > stack.get(i))
                 min = stack.get(i);
         }
     }
 }