Added Doubly_Linked_List under C and cleaned & organized the repo

Author: Avinash Kushwaha

ARMSTRONG.exe

@@ -0,0 +1,141 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct Node {
+    int data;
+    struct Node* next;
+    struct Node* prev;
+} Node;
+
+Node* head = NULL;  
+
+// Function to create a new node
+Node* createNode(int data) {
+    Node* newNode = (Node*)malloc(sizeof(Node));
+    newNode->data = data;
+    newNode->next = NULL;
+    newNode->prev = NULL;
+    return newNode;
+}
+
+// Function to add a node at the beginning
+void addNodeAtBeginning(int data) {
+    Node* newNode = createNode(data);
+    newNode->next = head;
+    if (head != NULL) {
+        head->prev = newNode;
+    }
+    head = newNode;
+}
+
+// Function to add a node at the end
+void addNodeAtEnd(int data) {
+    Node* newNode = createNode(data);
+    if (head == NULL) {
+        head = newNode;
+        return;
+    }
+    Node* temp = head;
+    while (temp->next != NULL) {
+        temp = temp->next;
+    }
+    temp->next = newNode;
+    newNode->prev = temp;
+}
+
+// Function to add a node at a specific position
+void addNodeAtPosition(int data, int position) {
+    if (position == 0) {
+        addNodeAtBeginning(data);
+        return;
+    }
+    
+    Node* newNode = createNode(data);
+    Node* temp = head;
+    for (int i = 0; temp != NULL && i < position - 1; i++) {
+        temp = temp->next;
+    }
+    
+    if (temp == NULL) {
+        printf("Position out of bounds.\n");
+        free(newNode);
+        return;
+    }
+    
+    newNode->next = temp->next;
+    newNode->prev = temp;
+    if (temp->next != NULL) {
+        temp->next->prev = newNode;
+    }
+    temp->next = newNode;
+}
+
+// Function to display the list
+void displayList() {
+    Node* temp = head;
+    if (temp == NULL) {
+        printf("List is empty.\n");
+        return;
+    }
+    while (temp != NULL) {
+        printf("%d ", temp->data);
+        temp = temp->next;
+    }
+    printf("\n");
+}
+
+// Main function for the CLI
+int main() {
+    int choice, data, position;
+
+    while (1) {
+        printf("1. Add Node at Beginning\n");
+        printf("2. Add Node at End\n");
+        printf("3. Add Node at Position\n");
+        printf("4. Display List\n");
+        printf("5. Exit\n");
+        printf("Enter your choice: ");
+        scanf("%d", &choice);
+
+        switch (choice) {
+            case 1:
+                printf("Enter data for the new node: ");
+                scanf("%d", &data);
+                addNodeAtBeginning(data);
+                break;
+
+            case 2:
+                printf("Enter data for the new node: ");
+                scanf("%d", &data);
+                addNodeAtEnd(data);
+                break;
+
+            case 3:
+                printf("Enter data for the new node: ");
+                scanf("%d", &data);
+                printf("Enter position to add the node: ");
+                scanf("%d", &position);
+                addNodeAtPosition(data, position);
+                break;
+
+            case 4:
+                displayList();
+                break;
+
+            case 5:
+                printf("Exiting program.\n");
+                // Free the list before exiting (optional)
+                while (head != NULL) {
+                    Node* temp = head;
+                    head = head->next;
+                    free(temp);
+                }
+                exit(0);
+
+            default:
+                printf("Invalid choice. Please try again.\n");
+        }
+    }
+
+    return 0;
+}