From 549ae7d6387e1166c8fe9c8aea81fd3c1d0f445d Mon Sep 17 00:00:00 2001
From: Sundeep4sandy <Yerramsetti.Sandeep15@gmail.com>
Date: Mon, 6 Apr 2026 18:30:07 -0500
Subject: [PATCH] PreCourse1Complete

---
 Exercise_1.js | 54 ++++++++++++++++-------------
 Exercise_2.js | 60 ++++++++++++++++++--------------
 Exercise_3.js | 95 ++++++++++++++++++++++++++++-----------------------
 3 files changed, 118 insertions(+), 91 deletions(-)

diff --git a/Exercise_1.js b/Exercise_1.js
index 207189ea0..557648021 100644
--- a/Exercise_1.js
+++ b/Exercise_1.js
@@ -1,33 +1,41 @@
 class Stack {
   //Please read sample.java file before starting.
   //Kindly include Time and Space complexity at top of each file
-​
-    constructor() {
-        //Initialize your constructor
-        this.MAX = 1000;
-        this.top = -1;
-        this.a = new Array(this.MAX);
+  constructor() {
+    //Initialize your constructor
+    this.MAX = 1000;
+    this.top = -1;
+    this.a = new Array(this.MAX);
+  }
+  isEmpty() {
+    return this.top === -1;
+  }
+  push(x) {
+    if (this.top >= this.MAX - 1) {
+      console.log("Stack Overflow");
+      return false;
     }
-​
-    function isEmpty() {
-        //Write your code here
+    this.top += 1;
+    this.a[this.top] = x;
+    return true;
+  }
+  pop() {
+    if (this.isEmpty()) {
+      console.log("Stack Underflow");
+      return 0;
     }
-​
-    function push(x) {
-        //Check for stack Overflow
-        //Write your code here
-    }
-​
-    function pop() {
-        //If empty return 0 and print " Stack Underflow"
-        //Write your code here
-    }
-​
-    function peek() {
-       //Write your code here
+    const val = this.a[this.top];
+    this.top -= 1;
+    return val;
+  }
+  peek() {
+    if (this.isEmpty()) {
+      console.log("Stack Empty");
+      return 0;
     }
+    return this.a[this.top];
+  }
 }
-​
 let s = new Stack();
 s.push(10);
 s.push(20);
diff --git a/Exercise_2.js b/Exercise_2.js
index 2e3216f94..471809d28 100644
--- a/Exercise_2.js
+++ b/Exercise_2.js
@@ -1,33 +1,43 @@
 class StackAsLinkedList {
-​
-    static stackNode = class {
-​
-        constructor(d) {
-            //Constructor here
-            this.data = d;
-            this.next = null;
-        }
+  static stackNode = class {
+    constructor(d) {
+      //Constructor here
+      this.data = d;
+      this.next = null;
     }
-​
-    function isEmpty() {
-        //Write your code here for the condition if stack is empty.
+  };
+  constructor() {
+    this.root = null; // top of the stack
+  }
+  isEmpty() {
+    return this.root === null;
+  }
+
+  push(data) {
+    const newNode = new StackAsLinkedList.stackNode(data);
+    newNode.next = this.root;
+    this.root = newNode;
+  }
+
+  pop() {
+    if (this.isEmpty()) {
+      console.log("Stack Underflow");
+      return 0;
     }
-​
-    function push(data) {
-       //Write code to push data to the stack.
-    }
-​
-    function pop() {
-       //If Stack Empty Return 0 and print "Stack Underflow"
-       //Write code to pop the topmost element of stack.
-       //Also return the popped element
-    }
-​
-    function peek() {
-       //Write code to just return the topmost element without removing it.
+    const popData = this.root.data;
+    this.root = this.root.next;
+    return popData;
+  }
+
+  peek() {
+    if (this.isEmpty()) {
+      console.log("Stack Empty");
+      return 0;
     }
+    return this.root.data;
+  }
 }
-//Driver code
+
 const sll = new StackAsLinkedList();
 sll.push(10);
 sll.push(20);
diff --git a/Exercise_3.js b/Exercise_3.js
index d1511f80e..336608563 100644
--- a/Exercise_3.js
+++ b/Exercise_3.js
@@ -1,49 +1,58 @@
-// Java program to implement
 // a Singly Linked List
 class LinkedList {
-    constructor() {
-        this.head = null;
+  constructor() {
+    this.startPos = null;
+  }
+  // Linked list Node.
+  static Node = class {
+    constructor(d) {
+      this.data = d;
+      this.next = null;
     }
-     // Linked list Node.
-     static Node = class {
-        constructor(d) {
-            this.data = d;
-            this.next = null;
-        }
+  };
+
+  // Method to insert a new node
+  insert(list, data) {
+    let newNode = new LinkedList.Node(data);
+
+    if (list.startPos === null) {
+      list.startPos = newNode;
+    } else {
+      let lastPos = list.startPos;
+      while (lastPos.next !== null) {
+        lastPos = lastPos.next;
+      }
+      lastPos.next = newNode;
     }
-​
-     // Method to insert a new node
-    function insert(list, data) {
-        // Create a new node with given 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
-    }
-​
-     // Method to print the LinkedList.
-    function printList(list) {
-        // Traverse through the LinkedList
-​
-        // Print the data at current node
-​
-        // Go to next node
+
+    return list;
+  }
+
+  // Method to print the LinkedList.
+  printList(list) {
+    let currNode = list.startPos;
+
+    let output = "";
+    while (currNode !== null) {
+      output += currNode.data + " ";
+      currNode = currNode.next;
     }
+    console.log(output.trim());
+
+    // Traverse through the LinkedList
+    // Print the data at current node
+    // Go to next node
+  }
 }
-       // Driver code
-       /* Start with the empty list. */
-       let list = new LinkedList();
-​
-        // ******INSERTION******
-        // Insert the values
-        list.insert(list, 1);
-        list.insert(list, 2);
-        list.insert(list, 3);
-        list.insert(list, 4);
-        // Print the LinkedList
-        list.printList(list);
+// Driver code
+/* Start with the empty list. */
+let list = new LinkedList();
+
+// ******INSERTION******
+// Insert the values
+list.insert(list, 1);
+list.insert(list, 2);
+list.insert(list, 3);
+list.insert(list, 4);
+// Print the LinkedList
+list.printList(list);