C Exercises: Convert a Doubly Linked list into a string

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

// Structure to define a doubly linked list node
struct node {
  int num;
  struct node *preptr;
  struct node *nextptr;
}*stnode, *ennode;

// Function prototypes
void DlListcreation(int n);
void DlList_str();

int main() {
  int n, num1, a, insPlc;
  stnode = NULL;
  ennode = NULL;

  printf(" Input the number of nodes: ");
  scanf("%d", &n);

  // Function call to create a doubly linked list
  DlListcreation(n);

  // Function call to convert the doubly linked list to a string
  DlList_str();
}

// Function to create a doubly linked list
void DlListcreation(int n) {
  int i, num;
  struct node *fnNode;

  if (n >= 1) {
    // Allocating memory for the first node
    stnode = (struct node *) malloc(sizeof(struct node));
    if (stnode != NULL) {
      printf(" Input data for node 1 : "); // assigning data in the first node
      scanf("%d", &num);
      stnode->num = num;
      stnode->preptr = NULL;
      stnode->nextptr = NULL;
      ennode = stnode;

      // Loop to create subsequent nodes and link them in the list
      for (i = 2; i <= n; i++) {
        fnNode = (struct node *) malloc(sizeof(struct node));
        if (fnNode != NULL) {
          printf(" Input data for node %d : ", i);
          scanf("%d", &num);
          fnNode->num = num;
          fnNode->preptr = ennode; // new node is linking with the previous node
          fnNode->nextptr = NULL; // set next address of fnnode is NULL
          ennode->nextptr = fnNode; // previous node is linking with the new node
          ennode = fnNode; // assign new node as the last node
        } else {
          printf(" Memory can not be allocated.");
          break;
        }
      }
    } else {
      printf(" Memory can not be allocated.");
    }
  }
}

// Function to convert the doubly linked list to a string
void DlList_str() {
  struct node *current;
  current = stnode;
  char text_str[100] = "";

  // Loop through the list and concatenate node data to a string
  while (current != NULL) {
    char str[10];
    sprintf(str, "%d", current->num);
    strcat(text_str, str);
    strcat(text_str, " ");    
    current = current->nextptr;
  }

  // Display the doubly linked list in string format
  printf("\nThe doubly linked list in string format: %s\n", text_str);
}