Doubly linked list program added

doubly_linked_list.cpp

@@ -0,0 +1,270 @@
+#include<iostream>
+#include<map>
+using namespace std;
+
+class Node {
+
+    public:
+    int data;
+    Node* next;
+
+
+    Node(int data) {
+        this -> data = data;
+        this -> next = NULL;
+    }
+
+
+    ~Node() {
+        int value = this -> data;
+
+        if(this->next != NULL) {
+            delete next;
+            this->next = NULL;
+        }
+        cout << " memory is free for node with data " << value << endl;
+    }
+
+};
+
+void insertAtHead(Node* &head, int d) {
+
+
+    Node* temp = new Node(d);
+    temp -> next = head;
+    head = temp;
+}
+
+void insertAtTail(Node* &tail, int d) {
+
+    Node* temp = new Node(d);
+    tail -> next = temp;
+    tail  = temp;
+}
+
+void print(Node* &head) {
+
+    if(head == NULL) {
+        cout << "List is empty "<< endl;
+        return ;
+    }
+    Node* temp = head;
+
+    while(temp != NULL ) {
+        cout << temp -> data << " ";
+        temp = temp -> next;
+    }
+    cout << endl;
+}
+
+void insertAtPosition(Node* &tail, Node* & head, int position, int d) {
+
+
+
+    if(position == 1) {
+        insertAtHead(head, d);
+        return;
+    }
+
+    Node* temp  = head;
+    int cnt = 1;
+
+    while(cnt < position-1) {
+        temp = temp->next;
+        cnt++;
+    }
+
+    if(temp -> next == NULL) {
+        insertAtTail(tail,d);
+        return ;
+    }
+
+
+    Node* nodeToInsert = new Node(d);
+
+    nodeToInsert -> next = temp -> next;
+
+    temp -> next = nodeToInsert;
+}
+
+void deleteNode(int position, Node* & head) { 
+
+
+    if(position == 1) {
+        Node* temp = head;
+        head = head -> next;
+
+        temp -> next = NULL;
+        delete temp;
+    }
+    else
+    {
+
+        Node* curr = head;
+        Node* prev = NULL;
+
+        int cnt = 1;
+        while(cnt < position) {
+            prev = curr;
+            curr = curr -> next;
+            cnt++;
+        }
+
+        prev -> next = curr -> next;
+        curr -> next  = NULL;
+        delete curr;
+
+    }
+}
+
+bool isCircularList(Node* head) {
+
+    if(head == NULL) {
+        return true;
+    }
+
+    Node* temp = head -> next;
+    while(temp != NULL && temp != head ) {
+        temp = temp -> next;
+    }
+
+    if(temp == head ) {
+        return true;
+    }
+
+    return false;
+}
+
+
+bool detectLoop(Node* head) {
+
+    if(head == NULL)
+        return false;
+
+    map<Node*, bool> visited;
+
+    Node* temp = head;
+
+    while(temp !=NULL) {
+
+
+        if(visited[temp] == true) {
+            cout << "Present on element " << temp->data << endl;
+            return true;
+        }
+
+        visited[temp] = true;
+        temp = temp -> next;
+
+    }
+    return false;
+
+}
+
+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) {
+            cout << "present at " << slow -> data << endl;
+            return slow;
+        }
+    }
+
+    return NULL;
+
+}
+
+Node* getStartingNode(Node* head) {
+
+    if(head == NULL) 
+        return NULL;
+
+    Node* intersection = floydDetectLoop(head);
+    Node* slow = head;
+
+    while(slow != intersection) {
+        slow = slow -> next;
+        intersection = intersection -> next;
+    }  
+
+    return slow;
+
+}
+
+void removeLoop(Node* head) {
+
+    if( head == NULL)
+        return;
+
+    Node* startOfLoop = getStartingNode(head);
+    Node* temp = startOfLoop;
+
+    while(temp -> next != startOfLoop) {
+        temp = temp -> next;
+    } 
+
+    temp -> next = NULL;
+
+}
+
+
+int main() {
+
+
+    Node* node1 = new Node(10);
+
+
+
+    Node* head = node1; 
+    Node* tail = node1;
+
+
+    insertAtTail(tail, 12);
+
+
+
+    insertAtTail(tail, 15);
+
+
+    insertAtPosition(tail,head, 4, 22);
+
+
+
+    tail -> next = head ->next;
+
+    cout << "head " << head -> data << endl;
+    cout << "tail " << tail -> data << endl;
+
+
+    if(floydDetectLoop(head) != NULL) {
+        cout << "Cycle is present " << endl;
+    }
+    else
+    {
+        cout << "no cycle" << endl;
+    }
+
+    Node* loop = getStartingNode(head);
+
+    cout << "loop starts at " << loop -> data  << endl;
+
+    removeLoop(head);
+    print(head);
+
+
+    return 0;
+}