ll.c

#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 * insert_top(int, Node *);
Node * insert_bottom(int, Node *);
Node * insert_after(int, int, Node *);
Node * insert_before(int, int, Node *);
void print(Node *);
int count(Node *);

/* Add a new node to the top of a list */
Node * insert_top(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;
}


/* Add a new node to the bottom of a list */
Node * insert_bottom(int num, Node *head) {
  Node *current_node = head;
  Node *new_node;
 while ( current_node != NULL && current_node->next != NULL) {
   current_node = current_node->next;
  }

  new_node = (Node *) malloc(sizeof(Node));
  new_node->data = num;
  new_node->next= NULL;
  if (current_node != NULL)
    current_node->next = new_node;
  else
     head = new_node;
return head;
}


/* Add a new node after an element in the list */
Node * insert_after(int num, int prev_num, Node *head) {
  Node *current_node = head;
  Node *new_node;
  while ( current_node->data != prev_num) {
      current_node = current_node->next;
  }
  new_node = (Node *) malloc(sizeof(Node));
  new_node->data = num;
  new_node->next= current_node->next;
  current_node->next = new_node;
return head;
}


/* Add a new node before an element in the list */
  Node * insert_before(int num, int next_num, Node *head) {
  Node *current_node = head;
  Node *new_node;
  while ( current_node->next->data != next_num) {
    current_node = current_node->next;
  }
  new_node = (Node *) malloc(sizeof(Node));
  new_node->data = num;
  new_node->next= current_node->next;
  current_node->next = 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;
  }
}

/* Program main */ 
int main()
{
   Node *head = NULL;
   int num, prev_num, next_num;
   int option;
   char * temp;
   char ch;
   /* Display Menu */
   while(1) {

     printf("\n ***********************************\n");
     printf("\n *  Linked list operations:        *\n");
     printf("\n *  1. Insert at the top of list   *\n");
     printf("\n *  2. Insert at bottom of list    *\n");
     printf("\n *  3. Insert after an element     *\n");
     printf("\n *  4. Insert before an element    *\n");
     printf("\n *  5. Show all elements           *\n");
     printf("\n *  6. Quit                        *\n");
     printf("\n ***********************************\n");
     printf("\n Choose an option [1-5] : ");
     if (scanf("%d", &option) != 1) {
        printf(" *Error: Invalid input. Try again.\n");
        scanf("%s", &temp); /*clear input buffer */
        continue;
     }

     switch (option) {
      case 1:        /* Add to top*/
          printf(" Enter a number to insert : ");
          if (scanf("%d", &num) != 1) {
              printf(" *Error: Invalid input.\n");
              scanf("%s", &temp);   /*clear input buffer */
              continue;
          }
          head = insert_top(num, head);
          printf("Number %d added to the top of the list", num);
          printf("\nPress any key to continue...");
          getch();
          break;

      case 2:    /* add to bottom */
          printf(" Enter a number to insert : ");
          if (scanf("%d", &num) != 1) {
              printf(" *Error: Invalid input. \n");
              scanf("%s", &temp); 
              continue;
          }
          head = insert_bottom(num, head);
          printf("%d added to the bottom of the list", num);
          printf("\nPress any key to continue...");
          getch();
          break;

      case 3:    /* Insert After */
          printf(" Enter a number to insert : ");
          if (scanf("%d", &num) != 1) {
              printf(" *Error: Invalid input.\n");
              scanf("%s", &temp);  
              continue;
          }

          printf(" After which number do you want to insert : ");
          if (scanf("%d", &prev_num) != 1) {
              printf(" *Error: Invalid input.\n");
              scanf("%s", &temp);
              continue;
          }
          if (head != NULL) {
              head = insert_after(num, prev_num, head);
              printf("%d is inserted after %d", num, prev_num);
          }else {
              printf("The list is empty", num, prev_num);
          }
              printf("\nPress any key to continue...");
              getch();
              break;

      case 4:    /* Insert Before */
           printf(" Enter a number to insert : ");
           if (scanf("%d", &num) != 1) {
              printf(" *Error: Invalid input. \n");
              scanf("%s", &temp);
              continue;
          }

          printf(" Before which number do you want to insert : ");
          if (scanf("%d", &prev_num) != 1) {
              printf(" *Error: Invalid input.\n");
              scanf("%s", &temp);
              continue;
          }

        if (head != NULL) {
             head = insert_before(num, prev_num, head);
             printf("Number %d inserted before %d", num, prev_num);
         }else {
             printf("The list is empty", num, prev_num);
         }
             printf("\nPress any key to continue...");
            getch();
            break;

      case 5: /* Show all elements */
          printf("\nElements in the list: \n [ ");
          print(head);
          printf("]\n\nPress any key to continue...");
          getch();
          break;

      case 6:  /* 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. Insert at the top of list   *
 *   2. Insert at bottom of list    *
 *   3. Insert after an element     *
 *   4. Insert before an element    *
 *   5. Show all elements           *
 *   6. Quit                        *
 ************************************

 Choose an option [1-5] : 4
 Enter a number to insert : 4
 Before which number do you want to insert : 5
Number 4 is now inserted before 5 in the list
Press any key to continue...

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Post a comment

Comments
nikhi | March 24, 2019 5:31 PM |

by compiling this there is arising an error: invalid type argument of ‘->’ (have ‘int’),what is meant by this.....
Suhetu | August 22, 2018 6:08 AM |

Bro, it's picking up garbage values when I want to show all the elements.
rizwana m | August 17, 2018 7:59 AM |

you to enter input for this program
Remy | December 13, 2017 10:55 AM |

thanks you so much
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