Single Linked List in C

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

struct node {
  int value;
  struct node *next;
};

void insert();
void display();
void delete();
int count();

typedef struct node DATA_NODE;

DATA_NODE *head_node, *first_node, *temp_node = 0, *prev_node, next_node;
int data;

int main() {
  int option = 0;

  printf("Singly Linked List Example - All Operations\n");

  while (option < 5) {

    printf("\nOptions\n");
    printf("1 : Insert into Linked List \n");
    printf("2 : Delete from Linked List \n");
    printf("3 : Display Linked List\n");
    printf("4 : Count Linked List\n");
    printf("Others : Exit()\n");
    printf("Enter your option:");
    scanf("%d", &option);
    switch (option) {
      case 1:
        insert();
        break;
      case 2:
        delete();
        break;
      case 3:
        display();
        break;
      case 4:
        count();
        break;
      default:
        break;
    }
  }

  return 0;
}

void insert() {
  printf("\nEnter Element for Insert Linked List : \n");
  scanf("%d", &data);

  temp_node = (DATA_NODE *) malloc(sizeof (DATA_NODE));

  temp_node->value = data;

  if (first_node == 0) {
    first_node = temp_node;
  } else {
    head_node->next = temp_node;
  }
  temp_node->next = 0;
  head_node = temp_node;
  fflush(stdin);
}

void delete() {
  int countvalue, pos, i = 0;
  countvalue = count();
  temp_node = first_node;
  printf("\nDisplay Linked List : \n");

  printf("\nEnter Position for Delete Element : \n");
  scanf("%d", &pos);

  if (pos > 0 && pos <= countvalue) {
    if (pos == 1) {
      temp_node = temp_node -> next;
      first_node = temp_node;
      printf("\nDeleted Successfully \n\n");
    } else {
      while (temp_node != 0) {
        if (i == (pos - 1)) {
          prev_node->next = temp_node->next;
          if(i == (countvalue - 1))
          {
     head_node = prev_node;
    }
          printf("\nDeleted Successfully \n\n");
          break;
        } else {
          i++;
          prev_node = temp_node;
          temp_node = temp_node -> next;
        }
      }
    }
  } else
    printf("\nInvalid Position \n\n");
}

void display() {
  int count = 0;
  temp_node = first_node;
  printf("\nDisplay Linked List : \n");
  while (temp_node != 0) {
    printf("# %d # ", temp_node->value);
    count++;
    temp_node = temp_node -> next;
  }
  printf("\nNo Of Items In Linked List : %d\n", count);
}

int count() {
  int count = 0;
  temp_node = first_node;
  while (temp_node != 0) {
    count++;
    temp_node = temp_node -> next;
  }
  printf("\nNo Of Items In Linked List : %d\n", count);
  return count;
}







Sample Output:

Singly Linked List Example - All Operations

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:1

Enter Element for Insert Linked List :
100

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:1

Enter Element for Insert Linked List :
200

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:1

Enter Element for Insert Linked List :
300

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:1

Enter Element for Insert Linked List :
400

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:1

Enter Element for Insert Linked List :
500

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:3

Display Linked List :
# 100 # # 200 # # 300 # # 400 # # 500 #
No Of Items In Linked List : 5

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:4

No Of Items In Linked List : 5

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:2

No Of Items In Linked List : 5

Display Linked List :

Enter Position for Delete Element :
3

Deleted Successfully


Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:3

Display Linked List :
# 100 # # 200 # # 400 # # 500 #
No Of Items In Linked List : 4

Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:2

No Of Items In Linked List : 4

Display Linked List :

Enter Position for Delete Element :
6

Invalid Position


Options
1 : Insert into Linked List
2 : Delete from Linked List
3 : Display Linked List
4 : Count Linked List
Others : Exit()
Enter your option:
5


------------------
(program exited with code: 0)

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