Question

Same problem as Problem 1 however you will implement the opposite of a MaxStack, namely MinStack. Design a stack class by importing the available java.util.Stack to have the following features:

• push(x) -- push element x onto stack, where x is anywhere between Integer.MIN_VALUE and Integer.MAX_VALUE.
• pop() -- remove the element on top of the stack.
• top() -- get the top element.
• getMin() -- retrieve the min element in the stack in constant time (i.e., O(1)).

Your code should have the following shape and form:

import java.util.Stack;
public class HomeworkAssignment1_2 {   
    public static void main(String[] args) {
       // just like Problem 1, whatever you need here
       // etc.
   }
}
// JUST LIKE ANY PROBLEM, YOUR STYLING AND DOCUMENTATION GOES HERE
// SEE PROBLEM 1 FOR EXAMPLE.
class MinStack {

   // Initialize your data structure here
   public MinStack() { // YOUR CODE HERE }

   public void push(int x) { // YOUR CODE HERE }
   public void pop() { // YOUR CODE HERE }
   public int top() { // YOUR CODE HERE }
   public int getMin() { // YOUR CODE HERE }
}

EXAMPLES

MinStack minStack = new minStack();

minStack.push(-2);

minStack.push(0);

minStack.push(-3);

minStack.getMin(); // returns -3

minStack.pop();

minStack.top(); // returns 0

minStack.getMin(); // returns -2

CONSTRAINTS AND ASSUMPTIONS

• For this problem you are ONLY allowed to use Java's reference class Stack . Failure to do so will receive 5 points off.
• MinStack does not mean elements have to be ordered in increasing or decreasing values in the Stack.

You solution should persist a global min value while maintaining the ability to transact on a Stack data structure wrapped in your MinStack class

Answer 1

screenshot

sample output

code

import java.util.Stack;

public class HomeworkAssignment1_2 {
   public static void main(String[] args) {
       MinStack minStack = new MinStack();
       minStack.push(-2);
       minStack.push(0);
       minStack.push(-3);
System.out.println(minStack.getMin() ); // returns -3
minStack.pop();
System.out.println(minStack.top()); // returns 0
System.out.println( minStack.getMin()); // returns -2
}
}
class MinStack {
// two stack one for stroing min and one for storing original value
   Stack<Integer> s;
   Stack<Integer> ms;
// initialize both stack as empty
   public MinStack() {
       s=new Stack<Integer>();
       ms=new Stack<Integer>();
   }

// push x as it is in one stack and min in one stack
   public void push(int x) {
       s.push(x);
       int temp=x;
       if(!ms.isEmpty())
           temp=ms.peek();

       x=x<temp?x:temp;
       ms.push(x);
   }

   public void pop() {
       if(s.isEmpty()){
           return;
       }
       s.pop();
       ms.pop();
   }
   public int top() {
       return s.peek();
   }
   public int getMin() {
       return ms.peek();
   }

}

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