Create Circular Linked List

Circular Linked List

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+#include<iostream>
+
+using namespace std;
+
+class Node {
+  public:
+    int key;
+  int data;
+  Node * next;
+
+  Node() {
+    key = 0;
+    data = 0;
+    next = NULL;
+  }
+  Node(int k, int d) {
+    key = k;
+    data = d;
+  }
+};
+
+class CircularLinkedList {
+  public:
+    Node * head;
+
+  CircularLinkedList() {
+    head = NULL;
+  }
+
+  // 1. CHeck if node exists using key value
+  Node * nodeExists(int k) {
+
+    Node * temp = NULL;
+    Node * ptr = head;
+
+    if (ptr == NULL) {
+      return temp;
+    } else {
+      do {
+        if (ptr -> key == k) {
+          temp = ptr;
+        }
+        ptr = ptr -> next;
+
+      } while (ptr != head);
+      return temp;
+    }
+
+    //return temp;
+  }
+
+  // 2. Append a node to the list
+  void appendNode(Node * new_node) {
+    if (nodeExists(new_node -> key) != NULL) {
+      cout << "Node Already exists with key value : " <<
+        new_node -> key <<
+        ". Append another node with different Key value" <<
+        endl;
+    } else {
+      if (head == NULL) {
+        head = new_node;
+        new_node -> next = head;
+        cout << "Node Appended at first Head position" << endl;
+      } else {
+        Node * ptr = head;
+        while (ptr -> next != head) {
+          ptr = ptr -> next;
+        }
+        ptr -> next = new_node;
+        new_node -> next = head;
+        cout << "Node Appended" << endl;
+      }
+    }
+
+  }
+  // 3. Prepend Node - Attach a node at the start
+  void prependNode(Node * new_node) {
+    if (nodeExists(new_node -> key) != NULL) {
+      cout << "Node Already exists with key value : " <<
+        new_node -> key <<
+        ". Append another node with different Key value" <<
+        endl;
+    } else {
+      if (head == NULL) {
+        head = new_node;
+        new_node -> next = head;
+        cout << "Node Prepended at first Head position" << endl;
+      } else {
+        Node * ptr = head;
+        while (ptr -> next != head) {
+          ptr = ptr -> next;
+        }
+
+        ptr -> next = new_node;
+        new_node -> next = head;
+        head = new_node;
+        cout << "Node Prepended" << endl;
+      }
+
+    }
+  }
+
+  // 4. Insert a Node after a particular node in the list
+  void insertNodeAfter(int k, Node * new_node) {
+    Node * ptr = nodeExists(k);
+    if (ptr == NULL) {
+      cout << "No node exists with key value OF: " << k << endl;
+    } else {
+      if (nodeExists(new_node -> key) != NULL) {
+        cout << "Node Already exists with key value : " <<
+          new_node -> key <<
+          ". Append another node with different Key value" <<
+          endl;
+      } else {
+        if (ptr -> next == head) {
+          new_node -> next = head;
+          ptr -> next = new_node;
+          cout << "Node Inserted at the End" << endl;
+        } else {
+          new_node -> next = ptr -> next;
+          ptr -> next = new_node;
+          cout << "Node Inserted in between" << endl;
+        }
+
+      }
+    }
+  }
+
+  // 5. Delete node by unique key
+  void deleteNodeByKey(int k) {
+    Node * ptr = nodeExists(k);
+    if (ptr == NULL) {
+      cout << "No node exists with key value OF : " << k <<
+        endl;
+    } else {
+
+      if (ptr == head) {
+        if (head -> next == NULL) {
+          head = NULL;
+          cout << "Head node Unlinked... List Empty";
+        } else {
+          Node * ptr1 = head;
+          while (ptr1 -> next != head) {
+            ptr1 = ptr1 -> next;
+          }
+          ptr1 -> next = head -> next;
+          head = head -> next;
+          cout << "Node UNLINKED with keys value : " << k << endl;
+        }
+      } else {
+        Node * temp = NULL;
+        Node * prevptr = head;
+        Node * currentptr = head -> next;
+        while (currentptr != NULL) {
+          if (currentptr -> key == k) {
+            temp = currentptr;
+            currentptr = NULL;
+          } else {
+            prevptr = prevptr -> next;
+            currentptr = currentptr -> next;
+          }
+        }
+
+        prevptr -> next = temp -> next;
+        cout << "Node UNLINKED with keys value : " << k << endl;
+
+      }
+
+    }
+
+  }
+  // 6th update node
+  void updateNodeByKey(int k, int new_data) {
+
+    Node * ptr = nodeExists(k);
+    if (ptr != NULL) {
+      ptr -> data = new_data;
+      cout << "Node Data Updated Successfully" << endl;
+    } else {
+      cout << "Node Doesn't exist with key value : " << k << endl;
+    }
+
+  }
+
+  // 7th printing
+  void printList() {
+    if (head == NULL) {
+      cout << "No Nodes in Circular Linked List";
+    } else {
+      cout << endl << "head address : " << head << endl;
+      cout << "Circular Linked List Values : " << endl;
+
+      Node * temp = head;
+
+      do {
+        cout << "(" << temp -> key << "," << temp -> data << "," << temp -> next << ") --> ";
+        temp = temp -> next;
+      } while (temp != head);
+    }
+
+  }
+
+};
+
+int main() {
+
+  CircularLinkedList obj;
+  int option;
+  int key1, k1, data1;
+  do {
+    cout << "\nWhat operation do you want to perform? Select Option number. Enter 0 to exit." << endl;
+    cout << "1. appendNode()" << endl;
+    cout << "2. prependNode()" << endl;
+    cout << "3. insertNodeAfter()" << endl;
+    cout << "4. deleteNodeByKey()" << endl;
+    cout << "5. updateNodeByKey()" << endl;
+    cout << "6. print()" << endl;
+    cout << "7. Clear Screen" << endl << endl;
+
+    cin >> option;
+    Node * n1 = new Node();
+    //Node n1;
+
+    switch (option) {
+    case 0:
+      break;
+    case 1:
+      cout << "Append Node Operation \nEnter key & data of the Node to be Appended" << endl;
+      cin >> key1;
+      cin >> data1;
+      n1 -> key = key1;
+      n1 -> data = data1;
+      obj.appendNode(n1);
+      //cout<<n1.key<<" = "<<n1.data<<endl;
+      break;
+
+    case 2:
+      cout << "Prepend Node Operation \nEnter key & data of the Node to be Prepended" << endl;
+      cin >> key1;
+      cin >> data1;
+      n1 -> key = key1;
+      n1 -> data = data1;
+      obj.prependNode(n1);
+      break;
+
+    case 3:
+      cout << "Insert Node After Operation \nEnter key of existing Node after which you want to Insert this New node: " << endl;
+      cin >> k1;
+      cout << "Enter key & data of the New Node first: " << endl;
+      cin >> key1;
+      cin >> data1;
+      n1 -> key = key1;
+      n1 -> data = data1;
+
+      obj.insertNodeAfter(k1, n1);
+      break;
+
+    case 4:
+
+      cout << "Delete Node By Key Operation - \nEnter key of the Node to be deleted: " << endl;
+      cin >> k1;
+      obj.deleteNodeByKey(k1);
+
+      break;
+    case 5:
+      cout << "Update Node By Key Operation - \nEnter key & NEW data to be updated" << endl;
+      cin >> key1;
+      cin >> data1;
+      obj.updateNodeByKey(key1, data1);
+
+      break;
+    case 6:
+      obj.printList();
+
+      break;
+    case 7:
+      system("cls");
+      break;
+    default:
+      cout << "Enter Proper Option number " << endl;
+    }
+
+  } while (option != 0);
+
+  return 0;
+}