C program to add, remove, print, and traverse a linked list

Updated on 15th September 2017

A linked list a data structure for storing a collection of data elements. The elements in the collection can be of any data type such as int, char, float etc., Linked lists store each data elements inside a node. A node consists of 2 fields - a data field which stores the actual data and pointer field which contains a pointer to the next node. So the first node (the node on the top of the list) contains some data and a pointer to the second node. The second node also contains some data and a pointer to the third node and so on. The last node in the list will point to NULL. A the pointer to the node at the top of the list is called head pointer. Here is an an example.

Singly Linked List
Singly Linked List Example

The linked list described above is also knows as a singly linked list as it has a single pointer that points to the next node. There are also other types of linked lists such as a doubly linked list which has pointers to both previous and next nodes.

Here is a C Program to perform the following operations on a singly linked list.

  • Add new elements to the top of the list.
  • Display all elements in the list.
  • Count the number of nodes in the list.
  • Remove all occurances of an element from the list.

This program also displays a menu for the users to make a selection. Here is the full source code.

Source Code

/*************************************************
 * C program to add, remove, count and		 *
 *	print the elements in a linked list	 *
 *************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

/* Node Stucture */
typedef struct node_t {
    int data;
    struct node_t *next;
} Node;

/* Function Declarations */
Node * add(int, Node *);
Node * remove(int, Node *);
void print(Node *);
int count(Node *);

/* Add a new node to linked list */
Node * add(int num, Node *head) {
    Node *new_node;
    new_node = (Node *) malloc(sizeof(Node));
    new_node->data = num;
    new_node->next= head;
    head = new_node;
return head;
}

/* Print all the elements in the linked list */
void print(Node *head) {
    Node *current_node = head;
   	while ( current_node != NULL) {
        printf("%d ", current_node->data);
        current_node = current_node->next;
    }
}

/* Count the number of nodes in a linked list */
int count(Node *head) {
    int cnt = 0;
    Node *current_node = head;
    while ( current_node != NULL) {
        cnt++;
        current_node = current_node->next;
    }
return(cnt);
}

/* Remove an element from a linked list */
Node * remove(int num, Node *head) {
    Node *current_node = head;
    Node *prev_node;
    int cnt = 0;
    while ( current_node != NULL) {
        if (current_node->data == num) {
            if (current_node == head) {
                 head = current_node->next;
            } else {
                prev_node->next = current_node->next;
            }
        } 
        prev_node = current_node;
        current_node = current_node->next;
    }
return(head);
}

/* Program main */ 
int main()
{

    Node *head = NULL;
    int num;
    int option;
    char * temp;

    /* Display Menu */
    while(1) {

        printf("\n ******************************************\n");
        printf("\n *  Linked list operations:               *\n");
        printf("\n *    1. Add                              *\n");
        printf("\n *    2. Remove                           *\n");
        printf("\n *    3. Count                            *\n");
        printf("\n *    4. Print                            *\n");    
        printf("\n *    5. Quit                             *\n");    
        printf("\n ******************************************\n");
        printf("\n Choose an option [1-5] : ");
        if (scanf("%d", &option) != 1) {
            printf(" *Error: Invalid input. Press try again.\n");
            scanf("%s", &temp); /*this will clear the input buffer */
            continue;
        }

        switch (option) {
            case 1:        /* Add */
                printf(" Enter a number to add : ");
                if (scanf("%d", &num) != 1) {
                    printf(" *Error: Invalid input. Only integer numbers are allowed\n");
                    scanf("%s", &temp);    /*this will clear the input buffer */
                    continue;
                }
                head = add(num, head);
                printf("Number %d is now added to the list", num);
                printf("\nPress any key to continue...");
                getch();
                break;

            case 2:    /* Remove */
                printf(" Enter a number to remove : ");
                if (scanf("%d", &num) != 1) {
                    printf(" *Error: Invalid input. Only integer numbers are allowed\n");
                    scanf("%s", &temp);    /*this will clear the input buffer */
                    continue;
                }
                head = remove(num, head);
                printf("Number %d is now removed from the list", num);
                printf("\nPress any key to continue...");
                getch();
                break;

            case 3:    /* Count */
                printf("\nYour linked list contains %d nodes", count(head));
                printf("\nPress any key to continue...");
                getch();
                break;

            case 4: /* Print */
                printf("\nYour linked list contains the following values: \n [ ");
                print(head);
                printf("]\n\nPress any key to continue...");
                getch();
                break;

            case 5:    /* Exit */
                return(0);
                break;

            default:
                printf("Invalid Option. Please Try again.");
                getch();

            } /* End of Switch */
    } /* End of While */

return(0);
}

Sample Output

****************************************** * Linked list operations: * * 1. Add * * 2. Remove * * 3. Count * * 4. Print * * 5. Quit * ****************************************** Choose an option [1-5] : 1 Enter a number to add : 25 Number 25 is now added to the list Press any key to continue...

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