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);
        }
    }
}