linked_list.cpp

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

struct node {
	int data;
	struct node * next;
} *head;
  
int count() {
  struct node * n;
  int c = 0;
  n = head;
  while (n != NULL) {
    n = n -> next;
    c++;
  }
  return c;
}

void append(int num) {
  struct node * temp, * right;
  temp = (struct node * ) malloc(sizeof(struct node));
  temp -> data = num;
  right = (struct node * ) head;
  while (right -> next != NULL)
    right = right -> next;
  right -> next = temp;
  right = temp;
  right -> next = NULL;
}

void add(int num) {
  struct node * temp;
  temp = (struct node * ) malloc(sizeof(struct node));
  temp -> data = num;
  if (head == NULL) {
    head = temp;
    head -> next = NULL;
  } else {
    temp -> next = head;
    head = temp;
  }
}

void addafter(int num, int loc) {
  int i;
  struct node * temp, * left, * right;
  right = head;
  for (i = 1; i < loc; i++) {
    left = right;
    right = right -> next;
  }
  temp = (struct node * ) malloc(sizeof(struct node));
  temp -> data = num;
  left -> next = temp;
  left = temp;
  left -> next = right;
  return;
}

int ddelete(int num) {
  struct node * temp, * prev;
  temp = head;
  while (temp != NULL) {
    if (temp -> data == num) {
      if (temp == head) {
        head = temp -> next;
        free(temp);
        return 1;
      } else {
        prev -> next = temp -> next;
        free(temp);
        return 1;
      }
    } else {
      prev = temp;
      temp = temp -> next;
    }
  }
  return 0;
}

void insert(int num) {
  int c = 0;
  struct node * temp;
  temp = head;
  if (temp == NULL) {
    add(num);
  } else {
    while (temp != NULL) {
      if (temp -> data < num)
        c++;
      temp = temp -> next;
    }
    if (c == 0)
      add(num);
    else if (c < count())
      addafter(num, ++c);
    else
      append(num);
  }
}



void display(struct node * r) {
  r = head;
  if (r == NULL) {
    return;
  }
  while (r != NULL) {
    printf("%d ", r -> data);
    r = r -> next;
  }
  printf("\n");
}

int main() {
  int i, num;
  struct node * n;
  head = NULL;
  while (1) {
    printf("Linked List Operations\n");
    printf("===============\n");
    printf("1.Insert\n");
    printf("2.Display\n");
    printf("3.Size\n");
    printf("4.Delete\n");
    printf("5.Exit\n");
    printf("Enter your choice : ");
    if (scanf("%d", & i) <= 0) {
      printf("Enter only an Integer\n");
      exit(0);
    } else {
      switch (i) {
      case 1:
        printf("Enter the number to insert : ");
        scanf("%d", & num);
        insert(num);
        break;
      case 2:
        if (head == NULL) {
          printf("List is Empty\n");
        } else {
          printf("Element(s) in the list are : ");
        }
        display(n);
        break;
      case 3:
        printf("Size of the list is %d\n", count());
        break;
      case 4:
        if (head == NULL)
          printf("List is Empty\n");
        else {
          printf("Enter the number to delete : ");
          scanf("%d", & num);
          if (ddelete(num))
            printf("%d deleted successfully\n", num);
          else
            printf("%d not found in the list\n", num);
        }
        break;
      case 5:
        return 0;
      default:
        printf("Invalid option\n");
      }
    }
    
  }
  return 0;
}