Done precourse-1

Exercise_1.java

@@ -1,46 +1,85 @@
-class Stack { 
+class Stack {
     //Please read sample.java file before starting.
-  //Kindly include Time and Space complexity at top of each file
-    static final int MAX = 1000; 
-    int top; 
-    int a[] = new int[MAX]; // Maximum size of Stack 
-
-    boolean isEmpty() 
-    { 
-        //Write your code here 
-    } 
-
-    Stack() 
-    { 
-        //Initialize your constructor 
-    } 
-
-    boolean push(int x) 
-    { 
+    //Kindly include Time and Space complexity at top of each file
+    // Time Complexity :O(1)
+// Space Complexity :O(n)
+// Did this code successfully run on Leetcode :
+// Any problem you faced while coding this :No
+
+
+// Your code here along with comments explaining your approach
+
+
+    static final int MAX = 1000;
+    int top;
+    int a[] = new int[MAX]; // Maximum size of Stack
+
+    boolean isEmpty()
+    {
+        //Write your code here
+        return(top < 0);
+
+    }
+
+    Stack()
+    {
+        //Initialize your constructor
+        top = 0;
+    }
+
+    boolean push(int x)
+    {
         //Check for stack Overflow
         //Write your code here
-    } 
-
-    int pop() 
-    { 
+        if(top == MAX){
+            System.out.println("Stack Overflow");
+            return false;
+        } else {
+            a[top] = x;
+            top++;
+            System.out.println("Pushed into stack " +x);
+            return true;
+        }
+    }
+
+    int pop()
+    {
         //If empty return 0 and print " Stack Underflow"
         //Write your code here
-    } 
-
-    int peek() 
-    { 
+        if(isEmpty()){
+            System.out.println("Stack Underflow");
+            return 0;
+        } else {
+            top--;
+            int x = a[top];
+            return x;
+        }
+    }
+
+    int peek()
+    {
         //Write your code here
-    } 
-} 
-
-// Driver code 
-class Main { 
-    public static void main(String args[]) 
-    { 
-        Stack s = new Stack(); 
-        s.push(10); 
-        s.push(20); 
-        s.push(30); 
-        System.out.println(s.pop() + " Popped from stack"); 
-    } 
+        if (isEmpty()) {
+            System.out.println("Stack Empty");
+            return 0;
+        } else {
+            int index = a[top];
+//            System.out.println("Top element is " +index);
+            return index;
+        }
+
+    }
+}
+
+// Driver code
+class Main {
+    public static void main(String args[])
+    {
+        Stack s = new Stack();
+        s.push(10);
+        s.push(20);
+        s.push(30);
+        System.out.println(s.pop() + " Popped from stack");
+        System.out.println(s.peek() + "Top element from stack");
+    }
 }

LinkedList.java

@@ -0,0 +1,84 @@
+import java.io.*;
+
+// Java program to implement 
+// a Singly Linked List 
+public class LinkedList {
+
+    Node head; // head of list 
+
+    // Linked list Node. 
+    // This inner class is made static 
+    // so that main() can access it 
+    static class Node {
+
+        int data;
+        Node next;
+
+        // Constructor 
+        Node(int d)
+        {
+            //Write your code here
+            data = d;
+            next = null;
+        }
+    }
+
+    // Method to insert a new node
+    public static LinkedList insert(LinkedList list, int data)
+    {
+        // Create a new node with given data
+        Node newNode = new Node(data);
+
+        // If the Linked List is empty,
+        // then make the new node as head
+        // Else traverse till the last node
+        // and insert the new_node there
+
+        // Insert the new_node at last node
+        // Return the list by head
+        if(list.head == null){
+            list.head = newNode;
+        } else {
+            Node last = list.head;
+            while(last.next != null){
+                last = last.next;
+            }
+            last.next = newNode;
+        }
+        return list;
+    }
+
+    // Method to print the LinkedList.
+    public static void printList(LinkedList list)
+    {
+        Node currentNode = list.head;
+        // Traverse through the LinkedList
+        while(currentNode!=null) {
+            // Print the data at current node
+            System.out.println("Current Node " + currentNode.data + " ");
+            // Go to next node
+            currentNode = currentNode.next;
+        }
+    }
+
+    // Driver code 
+    public static void main(String[] args)
+    {
+        /* Start with the empty list. */
+        LinkedList list = new LinkedList();
+
+        // 
+        // ******INSERTION****** 
+        // 
+
+        // Insert the values 
+        list = insert(list, 1);
+        list = insert(list, 2);
+        list = insert(list, 3);
+        list = insert(list, 4);
+        list = insert(list, 5);
+
+        // Print the LinkedList 
+        printList(list);
+    }
+}