Design Linked List

Author: alisamad1

Leetcode_Practice_Questions/LC_141.cpp

@@ -1,20 +1,41 @@
 #include<iostream>
-#include<vector>
-#include<algorithm>
 using namespace std;
-// Linked List Cycle
-bool hasCycle(ListNode *head){
+struct ListNode{
+    int data;
+    ListNode * next;
+    ListNode(int val){
+        data = val;
+        next = NULL;
+    }
+};
+bool hascycle(ListNode * head){
     if(head == NULL){
         return false;
     }
-    ListNode *fast = head;
-    ListNode *slow = head;
-    while(fast->next!=NULL && fast->next->next!=NULL){
+    ListNode * slow = head;
+    ListNode * fast = head;
+    while(fast->next != NULL && fast->next->next != NULL){
         fast = fast->next->next;
         slow = slow->next;
         if(fast == slow){
             return true;
         }
     }
     return false;
+}
+int main(){
+    ListNode * head = new ListNode(1);
+    head->next = new ListNode(2);
+    head->next->next = new ListNode(3);
+    head->next->next->next = new ListNode(4);
+    head->next->next->next->next = new ListNode(5);
+    head->next->next->next->next->next = head->next;
+    bool isCycle = hascycle(head);
+    if(isCycle){
+        cout << "The Linked List Contains Cycle. " << endl;
+    }
+    else{
+        cout << "The Linked List Does not contain a Cycle. " << endl;
+    }
+    return 0;
 }

Leetcode_Practice_Questions/LC_707.cpp

@@ -0,0 +1,123 @@
+#include <iostream>
+using namespace std;
+class Node {
+public:
+    int val;
+    Node* prev;
+    Node* next;
+    Node(int val) {
+        this->val = val;
+        prev = NULL;
+        next = NULL;
+    }
+};
+class MyLinkedList {
+public:
+    Node* head;
+    Node* tail;
+    MyLinkedList() {
+        head = NULL;
+        tail = NULL;
+    }
+    int get(int index) {
+        Node* temp = head;
+        int i = 0;
+        while (temp != NULL) {
+            if (i == index) return temp->val;
+            temp = temp->next;
+            i++;
+        }
+        return -1;
+    }
+    void addAtHead(int val) {
+        Node* newNode = new Node(val); // fixed: was hardcoded as 1
+        if (head == NULL) {
+            head = tail = newNode;
+        } else {
+            newNode->next = head;
+            head->prev = newNode;
+            head = newNode;
+        }
+    }
+    void addAtTail(int val) {
+        Node* newNode = new Node(val);
+        if (tail == NULL) {
+            head = tail = newNode;
+        } else {
+            tail->next = newNode;
+            newNode->prev = tail;
+            tail = newNode;
+        }
+    }
+    void addAtIndex(int index, int val) {
+        if (index == 0) {
+            addAtHead(val);
+            return;
+        }
+        Node* temp = head;
+        int i = 0;
+        while (temp != NULL && i < index) {
+            temp = temp->next;
+            i++;
+        }
+        if (temp == NULL && i == index) {
+            addAtTail(val);
+            return;
+        }
+        if (temp == NULL) return;
+        Node* newNode = new Node(val);
+        newNode->next = temp;
+        newNode->prev = temp->prev;
+        if (temp->prev != NULL)
+            temp->prev->next = newNode;
+        temp->prev = newNode;
+    }
+    void deleteAtIndex(int index) {
+        if (head == NULL) return;
+        Node* temp = head;
+        int i = 0;
+        while (temp != NULL && i < index) {
+            temp = temp->next;
+            i++;
+        }
+        if (temp == NULL) return;
+        if (temp->prev != NULL)
+            temp->prev->next = temp->next;
+        else
+            head = temp->next;
+        if (temp->next != NULL)
+            temp->next->prev = temp->prev;
+        else
+            tail = temp->prev;
+        delete temp;
+    }
+    void printList() {
+        Node* temp = head;
+        while (temp != NULL) {
+            cout << temp->val << " ";
+            temp = temp->next;
+        }
+        cout << endl;
+    }
+};
+int main() {
+    MyLinkedList* obj = new MyLinkedList();
+    obj->addAtHead(10);
+    obj->addAtTail(20);
+    obj->addAtTail(30);
+    obj->addAtIndex(1, 15); // List becomes 10->15->20->30
+    cout << "Current List: ";
+    obj->printList();
+    cout << "Element at index 2: " << obj->get(2) << endl; // Should print 20
+    obj->deleteAtIndex(1); // Delete value 15
+    cout << "After deleting index 1: ";
+    obj->printList(); // Should be 10->20->30
+    obj->deleteAtIndex(0); // Delete value 10
+    cout << "After deleting head: ";
+    obj->printList(); // Should be 20->30
+    obj->deleteAtIndex(10); // Invalid index, no change
+    cout << "After attempting to delete invalid index: ";
+    obj->printList();
+    delete obj;
+    return 0;
+}