FloydDetectLoop Question

Author: alisamad1

Linked_List/circular_linked_list1.cpp

@@ -0,0 +1,35 @@
+#include<iostream>
+using namespace std;
+struct Node{
+    int data;
+    Node * next;
+    Node(int val) : data(val), next(nullptr) {}
+};
+bool isCircularLinkedList(Node * head){
+    // if linked list is empty
+    if(head == nullptr){
+        return true;
+    }
+    // if one node is present 
+    Node * temp = head->next;
+    while(temp != nullptr && temp != head){
+        temp = temp->next;
+    }
+    if(temp == head){
+        return true;
+    }
+    return false;
+}
+int main(){
+    Node * head = new Node(2);
+    head->next = new Node(3);
+    head->next->next = new Node(4);
+    head->next->next->next = head;
+    if(isCircularLinkedList(head)){
+        cout << "Linked List is circular in Nature " << endl;
+    }
+    else{
+        cout << "Linked list is not circular in nature " << endl;
+    }
+    return 0;
+}

Linked_List/detect_and_remove_loop.cpp

@@ -0,0 +1,82 @@
+#include<iostream>
+using namespace std;
+struct Node{
+    int data;
+    Node * next;
+    Node(int val): data(val), next(nullptr) {}
+};
+Node* floydDetectLoop(Node* head) {
+    if(head == NULL)
+        return NULL;
+    Node* slow = head;
+    Node* fast = head;
+    while(slow != NULL && fast !=NULL) {
+        fast = fast -> next;
+        if(fast != NULL) {
+            fast = fast -> next;
+        }
+        slow = slow -> next;
+        if(slow == fast) {
+            return slow;
+        }
+    }
+    return NULL;
+}
+Node* getStartingNode(Node* head) {
+    if(head == NULL) 
+        return NULL;
+    Node* intersection = floydDetectLoop(head);
+    if(intersection == NULL)
+        return NULL;
+    Node* slow = head;
+    while(slow != intersection) {
+        slow = slow -> next;
+        intersection = intersection -> next;
+    }  
+    return slow;
+}
+Node *removeLoop(Node *head)
+{
+    if( head == NULL)
+        return NULL;
+    Node* startOfLoop = getStartingNode(head);
+    if(startOfLoop == NULL)
+        return head;
+    Node* temp = startOfLoop;
+    while(temp -> next != startOfLoop) {
+        temp = temp -> next;
+    } 
+    temp -> next = NULL;
+    return head;
+}
+int main(){
+    Node * head = new Node(1);
+    head->next = new Node(2);
+    head->next->next = new Node(3);
+    head->next->next->next = new Node(4);
+    head->next->next->next->next = new Node(5);
+    head->next->next->next->next->next = head->next; // Creating a loop for testing
+    cout << "Original Linked List (with loop): ";
+    Node* temp = head;
+    for(int i = 0; i < 7; ++i) { // Print a few nodes to show the loop
+        if(temp == nullptr) break;
+        cout << temp->data << " ";
+        temp = temp->next;
+    }
+    cout << "..." << endl;
+    Node* loopStart = getStartingNode(head);
+    if(loopStart != nullptr){
+        cout << "Loop starts at node with data: " << loopStart->data << endl;
+    } else {
+        cout << "No loop detected." << endl;
+    }
+    head = removeLoop(head);
+    cout << "Linked List after removing loop: ";
+    temp = head;
+    while(temp != nullptr){
+        cout << temp->data << " ";
+        temp = temp->next;
+    }
+    cout << endl;
+    return 0;
+}

Linked_List/detect_loop.cpp

@@ -0,0 +1,38 @@
+#include<iostream>
+using namespace std;
+#include<map>
+#include<vector>
+struct Node{
+    int data;
+    Node * next;
+    Node(int val) : data(val), next(nullptr) {}
+};
+bool detectLoop(Node * head){
+    if(head == nullptr){
+        return false;
+    }
+    map<Node*, bool> visited;
+    Node * temp = head;
+    while(temp != nullptr){
+        if(visited[temp] == true){
+            return true;
+        }
+        visited[temp] = temp->next;
+        temp = temp->next;
+    }
+    return false;
+}
+int main(){
+    Node * head = new Node(2);
+    head->next = new Node(3);
+    head->next->next = new Node(4);
+    head->next->next->next = new Node(5);
+    head->next->next->next->next = head->next;
+    if(detectLoop(head)){
+        cout << "We detect a loop in the linked list. " << endl;
+    }
+    else{
+        cout << "We do not detect a loop in a linked list " << endl;
+    }
+    return 0;
+}

Linked_List/floydcycledetect.cpp

@@ -0,0 +1,41 @@
+#include<iostream>
+using namespace std;
+struct Node{
+    int data;
+    Node * next;
+    Node(int val) : data(val), next(nullptr) {}
+};
+Node * floydDetectLoop(Node* head){
+    if(head == nullptr){
+        return nullptr;
+    }
+    Node * slow = head;
+    Node * fast = head;
+    while(slow != nullptr && fast != nullptr){
+        fast = fast->next;
+        if(fast != nullptr){
+            fast = fast->next;
+        }
+        slow = slow->next;
+        if(slow == fast){
+            return slow;
+        }
+    }
+    return nullptr;
+}
+int main(){
+    Node * head = new Node(1);
+    head->next = new Node(2);
+    head->next->next = new Node(3);
+    head->next->next->next = new Node(4);
+    head->next->next->next->next = new Node(5);
+    head->next->next->next->next->next = head->next;
+    Node * loop = floydDetectLoop(head);
+    if(loop != nullptr){
+        cout << "We detect a loop in the linked list. " << endl;
+    }
+    else{
+        cout << "We do not detect a loop in a linked list. " << endl;
+    }
+    return 0;
+}