Answer3.cpp

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;
}