C Exercises: Create a singly linked list and print it in reverse order

Last update on December 20 2024 13:18:30 (UTC/GMT +8 hours)

Write a program in C to create a singly linked list of n nodes and display it in reverse order.

Visual Presentation:

C Exercises: Pictorial: Create a singly linked list and print it in reverse order.

Sample Solution:

C Code:

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

// Structure for a node in a linked list
struct node {
    int num;                // Data of the node
    struct node *nextptr;   // Address of the next node
} *stnode;                  // Pointer to the starting node

// Function prototypes
void createNodeList(int n);     // Function to create the linked list
void reverseDispList();         // Function to reverse the linked list
void displayList();             // Function to display the linked list

// Main function
int main() {
    int n;

    // Displaying the purpose of the program
    printf("\n\n Linked List : Create a singly linked list and print it in reverse order :\n");
    printf("------------------------------------------------------------------------------\n");

    // Inputting the number of nodes for the linked list
    printf(" Input the number of nodes : ");
    scanf("%d", &n);

    // Creating the linked list with n nodes
    createNodeList(n);
    printf("\n Data entered in the list are : \n");		

    // Displaying the data entered in the linked list
    displayList();

    // Reversing the linked list
    reverseDispList();
    printf("\n The list in reverse are :  \n");

    // Displaying the reversed linked list
    displayList();

    return 0;
}

// Function to create a linked list with n nodes
void createNodeList(int n) {
    struct node *fnNode, *tmp;
    int num, i;

    // Allocating memory for the starting node
    stnode = (struct node *)malloc(sizeof(struct node));

    // Checking if memory allocation is successful
    if(stnode == NULL) {
        printf(" Memory can not be allocated.");
    } else {
        // Reading data for the starting node from user input
        printf(" Input data for node 1 : ");
        scanf("%d", &num);
        stnode->num = num;      
        stnode->nextptr = NULL; // Setting the next pointer to NULL
        tmp = stnode;

        // Creating n nodes and adding them to the linked list
        for(i = 2; i <= n; i++) {
            fnNode = (struct node *)malloc(sizeof(struct node));

            // Checking if memory allocation is successful
            if(fnNode == NULL) {
                printf(" Memory can not be allocated.");
                break;
            } else {
                // Reading data for each node from user input
                printf(" Input data for node %d : ", i);
                scanf(" %d", &num);

                fnNode->num = num;      // Setting the data for fnNode
                fnNode->nextptr = NULL; // Setting the next pointer to NULL

                tmp->nextptr = fnNode;  // Linking the current node to fnNode
                tmp = tmp->nextptr;     // Moving tmp to the next node
            }
        }
    }
}

// Function to reverse the linked list
void reverseDispList() {
    struct node *prevNode, *curNode;

    if(stnode != NULL) {
        prevNode = stnode;
        curNode = stnode->nextptr;
        stnode = stnode->nextptr;

        prevNode->nextptr = NULL; // Convert the first node as last

        while(stnode != NULL) {
            stnode = stnode->nextptr;
            curNode->nextptr = prevNode;

            prevNode = curNode;
            curNode = stnode;
        }
        stnode = prevNode; // Convert the last node as head
    }
}

// Function to display the linked list
void displayList() {
    struct node *tmp;
    if(stnode == NULL) {
        printf(" No data found in the list.");
    } else {
        tmp = stnode;
        while(tmp != NULL) {
            printf(" Data = %d\n", tmp->num);   // Prints the data of current node
            tmp = tmp->nextptr;                 // Advances the position of current node
        }
    }
}

Sample Output:

 Linked List : Create a singly linked list and print it in reverse order :                                    
------------------------------------------------------------------------------                                
 Input the number of nodes : 3                                                                                
 Input data for node 1 : 5                                                                                    
 Input data for node 2 : 6                                                                                    
 Input data for node 3 : 7                                                                                    
                                                                                                              
 Data entered in the list are :                                                                               
 Data = 5                                                                                                     
 Data = 6                                                                                                     
 Data = 7                                                                                                     
                                                                                                              
 The list in reverse are :                                                                                    
 Data = 7                                                                                                     
 Data = 6                                                                                                     
 Data = 5

Flowchart: