Create Stack-Stack Using LL

Author: mmuskan22

Stack-Stack Using LL

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+Implement a Stack Data Structure specifically to store integer data using a Singly Linked List.
+The data members should be private.
+You need to implement the following public functions :
+1. Constructor:
+It initialises the data members as required.
+2. push(data) :
+This function should take one argument of type integer. It pushes the element into the stack and returns nothing.
+3. pop() :
+It pops the element from the top of the stack and in turn, returns the element being popped or deleted. In case the stack is empty, it returns -1.
+4. top :
+It returns the element being kept at the top of the stack. In case the stack is empty, it returns -1.
+5. size() :
+It returns the size of the stack at any given instance of time.
+6. isEmpty() :
+It returns a boolean value indicating whether the stack is empty or not.
+Operations Performed on the Stack:
+Query-1(Denoted by an integer 1): Pushes an integer data to the stack.
+
+Query-2(Denoted by an integer 2): Pops the data kept at the top of the stack and returns it to the caller.
+
+Query-3(Denoted by an integer 3): Fetches and returns the data being kept at the top of the stack but doesn't remove it, unlike the pop function.
+
+Query-4(Denoted by an integer 4): Returns the current size of the stack.
+
+Query-5(Denoted by an integer 5): Returns a boolean value denoting whether the stack is empty or not.
+Input Format:
+The first line contains an integer 'q' which denotes the number of queries to be run against each operation in the stack. 
+Then the test cases follow.
+
+Every 'q' lines represent an operation that needs to be performed.
+
+For the push operation, the input line will contain two integers separated by a single space, representing the type of the operation in integer and the integer data being pushed into the stack.
+
+For the rest of the operations on the stack, the input line will contain only one integer value, representing the query being performed on the stack.
+ Output Format:
+For Query-1, you do not need to return anything.
+For Query-2, prints the data being popped from the stack.
+For Query-3, prints the data kept on the top of the stack.
+For Query-4, prints the current size of the stack.
+For Query-5, prints 'true' or 'false'(without quotes).
+
+Output for every query will be printed in a separate line.
+Note:
+You are not required to print anything explicitly. It has already been taken care of. Just implement the function.
+ Constraints:
+1 <= q <= 10^5
+1 <= x <= 5
+-2^31 <= data <= 2^31 - 1 and data != -1
+
+Where 'q' is the total number of queries being performed on the stack, 'x' is the range for every query and data represents the integer pushed into the stack. 
+
+Time Limit: 1 second
+Sample Input 1:
+6
+1 13
+1 47
+4
+5
+2
+3
+Sample Output 1:
+2
+false
+47
+13
+Sample Input 2:
+4
+5
+2
+1 10
+5
+Sample Output 2:
+true
+-1
+false
+ Explanation of Sample Input 2:
+There are 4 queries in total.
+The first one is Query-5: It tells whether the stack is empty or not. Since the stack is empty at this point, the output is  'true'.
+
+The second one is Query-2: It pops the data from the stack. Since at this point in time, no data exist in the stack hence, it prints -1.
+
+The third one is Query-1: It pushes the specified data 10 into the stack and since the function doesn't return anything, nothing is printed.
+
+The fourth one is Query-5: It tells whether the stack is empty at this point or not. Since the stack has one element and hence it is not empty, false is printed.
+
+***********************************************************Code********************************************************
+
+public class Stack {
+
+    //Define the data members
+    private Node head;
+    private int size;
+   
+
+    public Stack() {
+        //Implement the Constructor
+        head=null;
+        size=0;
+    }
+
+
+
+    /*----------------- Public Functions of Stack -----------------*/
+
+
+    public int getSize() { 
+        return size;
+        //Implement the getSize() function
+    }
+
+    public boolean isEmpty() {
+        //Implement the isEmpty() function
+        return size==0;
+    }
+
+    public void push(int element) {
+        //Implement the push(element) function
+        Node newNode=new Node(element);
+        if (head==null)
+        {
+            head=newNode;
+        }
+        else
+        {
+           newNode.next=head;
+            head=newNode;
+        }
+        size++;
+    }
+
+    public int pop() {
+        //Implement the pop() function
+        if(head==null)
+            return -1;
+        int temp=head.data;
+        head=head.next;
+        size--;
+        return temp;
+    }
+
+    public int top() {
+        //Implement the top() function
+        if(head==null)
+            return -1;
+        return head.data;
+    }
+}