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Number of nodes in a singly linked list

Now let us write a function to count the number of nodes in a singly linked list.

This one is pretty simple.
  • traverse the list from first node
  • increment count after each node
  • count at the end of traversal is the number of nodes

 int get_count(NODEPTR temp)
 {
      int c = 0;
      while(temp)
      {
    c++;
    temp = temp->next;
      }
     return c; 
}

The function starts with head node and loops till temp becomes NULL. Please remember that NULL has a numerical value of 0 and 0 is false and the condition (temp) is as good as saying (temp!=NULL).

How about a recursive function for the same?


int get_count_recursive(NODEPTR temp)
{
    if(temp!=NULL)
 {
    return get_count_recursive(temp->next)+1;
        }
}

Time to write the driver program for this function

#include<stdio.h>  
#include<stdlib.h>
 struct node  
 {  
   int n;  
   struct node *next;   
 };  
 typedef struct node * NODEPTR;  
  
 NODEPTR create_node(int value)  
 {  
   NODEPTR temp = (NODEPTR) malloc(sizeof(struct node));  
    temp->next = NULL;  
   temp->n = value;  
   return temp;  
 } 

  
 NODEPTR append_node(NODEPTR head, NODEPTR newnode)  
 {  
    NODEPTR temp = head;
    if(temp==NULL)
      return newnode;
    while(temp->next !=NULL)
 temp = temp->next;
    temp->next = newnode;
    return head;  
 } 

 
 void display_nodes(NODEPTR head)  
 {  
   NODEPTR temp = head;//redundant 
   while (temp!= NULL)  
   {  
     printf("%d====>",temp->n);  
     temp = temp->next;  
   }  
   printf("\n");
 } 

 int get_count(NODEPTR temp)
 {
 int c = 0;
      while(temp)
        {
    c++;
    temp = temp->next;
        }
     return c; 
}
int get_count_recursive(NODEPTR temp)
{
    if(temp!=NULL)
 {
    return get_count_recursive(temp->next)+1;
        }
}
 
 int main()  
 {  
     NODEPTR head;  
     NODEPTR newnode,dnode;       
     //initialize head  
     head =  NULL;        
     while(1){
       int value;  
       NODEPTR newnode;  
       printf("node value (-1 to stop)=");  
       scanf("%d",&value); 
       if(value==-1) 
   break; 
       newnode = create_node(value);  
       head = append_node(head,newnode);      
     }
     printf("The linked list now is ");  
     display_nodes(head);
     printf("The number of nodes in sll is %d\n",get_count(head));
     printf("The number of nodes in sll using recursion is %d\n",get_count(head));
           
 }

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