Program to find size of Doubly Linked List

Given a doubly linked list, the task is to find the size of that doubly linked list. For example, size of below linked list is 4.

dll



A doubly linked list is a linked data structure that consists of a set of sequentially linked records called nodes. Each node contains two fields, called links, that are references to the previous and to the next node in the sequence of nodes.
Traversal of a doubly linked list can be in either direction. In fact, the direction of traversal can change many times, if desired.

For example the function should return 3 for the above doubly linked list.

Algorithm :

1) Initialize size to 0.
2) Initialize a node pointer, temp = head.
3) Do following while temp is not NULL
……a) temp = temp -> next
……b) size++;
4) Return size.

// A complete working C++ program to
// find size of doubly linked list.
#include <bits/stdc++.h>
using namespace std;

// A linked list node
struct Node
{
    int data;
    struct Node *next;
    struct Node *prev;
};

/* Function to add a node to front of doubly
   linked list */
void push(struct Node** head_ref, int new_data)
{
    struct Node* new_node = new Node;
    new_node->data  = new_data;
    new_node->next = (*head_ref);
    new_node->prev = NULL;
    if ((*head_ref) !=  NULL)
      (*head_ref)->prev = new_node ;
    (*head_ref)    = new_node;
}

// This function returns size of linked list
int findSize(struct Node *node)
{
   int res = 0;
   while (node != NULL)
   {
       res++;
       node = node->next;
   }
   return res;
}

/* Drier program to test above functions*/
int main()
{
    struct Node* head = NULL;
    push(&head, 4);
    push(&head, 3);
    push(&head, 2);
    push(&head, 1);
    cout << findSize(head);
    return 0;
}
Output:

4


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