Started LinkedList

TORRYNN · TORRYNN · Jun 17, 2025 · Jun 17, 2025 · Jun 17, 2025 · 2aa667e48c4bfdd1f6c67338c4aac1d49b799113
commit 2aa667e48c4bfdd1f6c67338c4aac1d49b799113
diff --git a/29_LinkedList/linked$Node.class b/29_LinkedList/linked$Node.class
diff --git a/29_LinkedList/linked.class b/29_LinkedList/linked.class
diff --git a/29_LinkedList/linked.java b/29_LinkedList/linked.java
@@ -0,0 +1,268 @@
+
+public class linked {
+    // head is a reference variable that is currently referring to null and it can
+    // only refer to the object of type node.
+    public static Node head;
+    // tail is also a reference variable that is currently referring to null.
+    public static Node tail;
+
+    public static int size;
+
+    public static class Node {
+        // data to store the value or data
+        int data;
+        // next store the address of the next node.
+        Node next;
+
+        public Node(int data) {
+            this.data = data;
+            this.next = null;
+        }
+
+    }
+
+    public void addFirst(int data) {
+        // Step1: Create new node
+        Node newNode = new Node(data);
+        size++;
+        if (head == null) {
+            head = tail = newNode;
+            return;
+        }
+
+        // Step2:Both newNode-> next and head is pointing to the same node
+        newNode.next = head;
+        // Step3: Updated the head now head is pointing to he newNode or we can say head
+        // is having the reference of newNode.
+        head = newNode;
+    }
+
+    public void addLast(int data) {
+        Node newNode = new Node(data);
+        size++;
+        if (head == null) {
+            head = tail = newNode;
+        }
+        ;
+        tail.next = newNode;
+        tail = newNode;
+    }
+
+    public void print() {
+        // Base Condition if LL is empty
+        if (head == null) {
+            System.out.print("");
+            return;
+        }
+        // Created a temporary reference that points to what head is pointing
+        Node temp = head;
+        // if our temp becomes null it means we reached end of LL
+        while (temp != null) {
+            // Printing data
+            System.out.print(temp.data + "->");
+            // Updating temp to point to next node.
+            temp = temp.next;
+        }
+        System.out.println("null");
+    }
+
+    // Add in a middle
+    public void add(int index, int data) {
+        if (index == 0) {
+            addFirst(data);
+            return;
+        }
+        Node newNode = new Node(data);
+        size++;
+        Node temp = head;
+        int i = 0;
+        while (i < index - 1) {
+            temp = temp.next;
+            i++;
+
+        }
+        newNode.next = temp.next;
+        temp.next = newNode;
+
+    }
+
+    public int removeFirst() {
+        if (size == 0) {
+            System.out.println("Linked- list is empty");
+            return Integer.MIN_VALUE;
+        } else if (size == 1) {
+            int val = head.data;
+            head = tail = null;
+            size = 0;
+            return val;
+        }
+        int val = head.data;
+
+        head = head.next;
+        size--;
+        return val;
+    }
+
+    public int removeLast() {
+        if (size == 0) {
+            System.out.println("Linked- list is empty");
+            return Integer.MIN_VALUE;
+        } else if (size == 1) {
+            int val = head.data;
+            head = tail = null;
+            size = 0;
+            return val;
+        }
+        Node prev = head;
+
+        for (int i = 0; i < size - 2; i++) {
+            prev = prev.next;
+        }
+        int val = prev.next.data;
+        prev.next = null;
+        tail = prev;
+        size--;
+        return val;
+    }
+
+    public int isearch(int key) {
+        // A tracker to iterate the linkedlist
+        Node temp = head;
+        // Variable to store index
+        int i = 0;
+        while (temp != null) {
+            // If key exist
+            if (temp.data == key) {
+                return i;
+            }
+            temp = temp.next;
+            i++;
+        }
+        return -1;
+    }
+
+    // Search in a linkedlist using Recursion
+    public int helper(Node head, int key) {
+        if (head == null) {
+            return -1;
+        }
+        if (head.data == key) {
+            return 0;
+        }
+        int idx = helper(head.next, key);
+        if (idx == -1) {
+            return -1;
+        }
+        return idx + 1;
+    }
+    public int rSearch(int key) {
+        return helper(head, key);
+    }
+
+=
+
+    // Iterative Approach with Time Complexity is O(n);
+    public void reverse() {
+        // Pointer to keep track of the previous node,
+        Node prev = null;
+        // Pointer to the current node being processed.
+        Node curr = tail = head;
+        // Temporary pointer to store the next node.
+        Node next;
+        // Traverse the list until all nodes are reversed(curr becomes null)
+        while (curr != null) {
+            // Store the next node before breaking the link
+            next = curr.next;
+            // Reverse the link by pointing the current node to previous node.
+            curr.next = prev;
+            // Move prev one step forward to current node.
+            prev = curr;
+            // Move curr one step forward to the next node.
+            curr = next;
+
+        }
+        head = prev;
+    }
+
+    // Approach 1: Iterative
+    public void deleteNthFromEnd(int idx) {
+        // Calculating the size of Linkedlist
+        Node temp = head;
+        int size = 0;
+        while (temp != null) {
+            temp = temp.next;
+            size++;
+
+        }
+
+        // Base Condition: If the idx is n means we have to remove first node
+        if (idx == size) {
+            head = head.next;
+            return;
+        }
+
+        int pos = size - idx;
+        Node prev = head;
+        while (--pos > 0) {
+            prev = prev.next;
+
+        }
+        prev.next = prev.next.next;
+        return;
+    }
+
+    // Approach2: Slow and Fast Pointer
+    public void deleteNthFromEnd2(int idx) {
+        // Pointer to calculate the previous positon of node
+        Node fast = head;
+        for (int i = 0; i < idx; i++) {
+            fast = fast.next;
+        }
+        if (fast == null) {
+            head = head.next;
+            return;
+        }
+        // Pointer to get the previous node of the node to be deleted
+        Node slow = head;
+        while (fast.next != null) {
+            fast = fast.next;
+            slow = slow.next;
+
+        }
+        slow.next = slow.next.next;
+        return;
+
+    }
+
+
+
+    public static void main(String[] args) {
+        linked ll = new linked();
+        ll.print();
+        ll.addFirst(2);
+        ll.print();
+        ll.addFirst(1);
+        ll.print();
+        ll.addLast(3);
+        ll.print();
+        ll.addLast(4);
+        ll.print();
+        ll.add(3, 9);
+        ll.print();
+        System.out.println(ll.size);
+        System.out.println(ll.removeFirst());
+        ll.print();
+        System.out.println(ll.removeLast());
+        ll.print();
+        System.out.println(ll.size);
+        ll.print();
+        System.out.println(ll.isearch(3));
+        System.out.println(ll.rSearch(3));
+        ll.reverse();
+        ll.print();
+        ll.deleteNthFromEnd(1);
+        ll.print();
+        ll.deleteNthFromEnd2(1);
+        ll.print();
+    }
+}
diff --git a/29_LinkedList/tempCodeRunnerFile.java b/29_LinkedList/tempCodeRunnerFile.java
@@ -0,0 +1 @@
+null
diff --git a/file_structure.txt b/file_structure.txt