Count nodes in Circular linked list
Given a circular linked list, count the number of nodes in it. For example, the output is 5 for the below list.
We use the concept used in Circular Linked List | Set 2 (Traversal). While traversing, we keep track of the count of nodes.
C++
// C++ program to count number of nodes in a circular// linked list.#include <bits/stdc++.h>using namespace std; /*structure for a node*/ struct Node { int data; Node* next; Node(int x) { data = x; next = NULL; }};/* Function to insert a node at the beginningof a Circular linked list */struct Node* push(struct Node* last, int data){ if (last == NULL) { struct Node* temp = (struct Node*)malloc(sizeof(struct Node)); // Assigning the data. temp->data = data; last = temp; // Note : list was empty. We link single node // to itself. temp->next = last; return last; } // Creating a node dynamically. struct Node* temp = (struct Node*)malloc(sizeof(struct Node)); // Assigning the data. temp->data = data; // Adjusting the links. temp->next = last->next; last->next = temp; return last;} /* Function to count nodes in a given Circularlinked list */ int countNodes(Node* head){ Node* temp = head; int result = 0; if (head != NULL) { do { temp = temp->next; result++; } while (temp != head); } return result;} /* Driver program to test above functions */int main(){ /* Initialize lists as empty */ Node* head = NULL; head = push(head, 12); head = push(head, 56); head = push(head, 2); head = push(head, 11); cout << countNodes(head); return 0;} // This code is contributed by anushikaseth |
C
// C program to count number of nodes in a circular linked// list.#include <stdio.h>#include <stdlib.h> /*structure for a node*/typedef struct Node { int data; struct Node* next;} Node; /* Function to insert a node at the beginning of a Circular linked list */void push(Node** head_ref, int data){ Node* ptr1 = (Node*)malloc(sizeof(Node)); Node* temp = *head_ref; ptr1->data = data; ptr1->next = *head_ref; /* If linked list is not NULL then set the next of last * node */ if (*head_ref != NULL) { while (temp->next != *head_ref) temp = temp->next; temp->next = ptr1; } else ptr1->next = ptr1; /*For the first node */ *head_ref = ptr1;} /* Function to count nodes in a given Circularlinked list */ int countNodes(Node* head){ Node* temp = head; int result = 0; if (head != NULL) { do { temp = temp->next; result++; } while (temp != head); } return result;} /* Driver program to test above functions */int main(){ /* Initialize lists as empty */ Node* head = NULL; push(&head;, 12); push(&head;, 56); push(&head;, 2); push(&head;, 11); printf("%d", countNodes(head)); return 0;} // This code is contributed by Aditya Kumar (adityakumar129) |
Java
// Java program to count number of nodes in // a circular linked list. class GFG{ /* ure for a node */static class Node{ int data; Node next; }; /* Function to insert a node at the beginning of a Circular linked list */static Node push( Node head_ref, int data) { Node ptr1 = new Node(); Node temp = head_ref; ptr1.data = data; ptr1.next = head_ref; /* If linked list is not null then set the next of last node */ if (head_ref != null) { while (temp.next != head_ref) temp = temp.next; temp.next = ptr1; } else ptr1.next = ptr1; /*For the first node */ head_ref = ptr1; return head_ref;} /* Function to print nodes in a given Circular linked list */static int countNodes( Node head) { Node temp = head; int result = 0; if (head != null) { do { temp = temp.next; result++; } while (temp != head); } return result; } /* Driver program to test above functions */public static void main(String args[]){ /* Initialize lists as empty */ Node head = null; head = push(head, 12); head = push(head, 56); head = push(head, 2); head = push(head, 11); System.out.printf("%d", countNodes(head)); }} // This code is contributed by Arnab Kundu |
Python3
# Python3 program to count number of nodes in# a circular linked list. # structure for a nodeclass Node: def __init__(self, data): self.data = data self.next = None # Function to insert a node at the beginning# of a Circular linked list */def push(head_ref,data): ptr1 = Node(0) temp = head_ref ptr1.data = data ptr1.next = head_ref # If the linked list is not None then set # the next of last node if (head_ref != None) : while (temp.next != head_ref): temp = temp.next temp.next = ptr1 else: ptr1.next = ptr1 #For the first node */ head_ref = ptr1 return head_ref # Function to print nodes # in a given Circular linked list def countNodes(head): temp = head result = 0 if (head != None) : while True : temp = temp.next result = result + 1 if (temp == head): break return result # Driver Code if __name__=='__main__': # Initialize lists as empty */ head = None head = push(head, 12) head = push(head, 56) head = push(head, 2) head = push(head, 11) print( countNodes(head)) # This code is contributed by Arnab Kundu |
C#
// C# program to count number of nodes in // a circular linked list. using System; class GFG { /* structure for a node */public class Node { public int data; public Node next; }; /* Function to insert a node at the beginning of a Circular linked list */static Node push( Node head_ref, int data) { Node ptr1 = new Node(); Node temp = head_ref; ptr1.data = data; ptr1.next = head_ref; /* If linked list is not null then set the next of last node */ if (head_ref != null) { while (temp.next != head_ref) temp = temp.next; temp.next = ptr1; } else ptr1.next = ptr1; /*For the first node */ head_ref = ptr1; return head_ref; } /* Function to print nodes in a given Circular linked list */static int countNodes( Node head) { Node temp = head; int result = 0; if (head != null) { do { temp = temp.next; result++; } while (temp != head); } return result; } /* Driver code */public static void Main(String []args) { /* Initialize lists as empty */ Node head = null; head = push(head, 12); head = push(head, 56); head = push(head, 2); head = push(head, 11); Console.Write( countNodes(head)); } } // This code is contributed by Arnab Kundu |
Javascript
<script>// javascript program to count number of nodes in // a circular linked list. /* ure for a node */class Node { constructor() { this.data = 0; this.next = null; }} /* * Function to insert a node at the beginning of a Circular linked list */ function push(head_ref , data) { var ptr1 = new Node(); var temp = head_ref; ptr1.data = data; ptr1.next = head_ref; /* * If linked list is not null then set the next of last node */ if (head_ref != null) { while (temp.next != head_ref) temp = temp.next; temp.next = ptr1; } else ptr1.next = ptr1; /* For the first node */ head_ref = ptr1; return head_ref; } /* * Function to print nodes in a given Circular linked list */ function countNodes(head) { var temp = head; var result = 0; if (head != null) { do { temp = temp.next; result++; } while (temp != head); } return result; } /* Driver program to test above functions */ /* Initialize lists as empty */ var head = null; head = push(head, 12); head = push(head, 56); head = push(head, 2); head = push(head, 11); document.write(countNodes(head)); // This code contributed by umadevi9616</script> |
Output
4
Time Complexity: O(n), As we are visiting every node just once.
Auxiliary Space: O(1), As constant extra space is used
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