q1.c

/*
1. Suppose that an ordered list of numbers is implemented by means of an array, Write a C program using separate functions to 
   i.      Insert a number
   ii.     Delete an element
   iii.    Reverse the list
*/
#include <stdio.h>

void array_print(int *a, size_t size)
{
  while(size--)
    printf("%i ",*a++);
}

int array_insert(int *a, size_t size, int element, size_t position)
/* Inserts the `element' to the array `a'.The`size' denotes the number of current elements in the array. The `element' is inserted at a[position].
The `size' should not be the size of the array allocated.
The function will check if the position specified is within the size specified.
It returns a positive integer if the insertion was successful else returns a false
with the error printed on stderr*/
{
  if (position >=size)
    {
      fprintf(stderr,"\narray_insert: The specified position %i is not less than the"
	      " size of the array which is %i\n",position,size);
      return 0;
    }
  int *p=a+position;//the pointer to the location where the new element will get inserted
  a+=size;//a points to one past the last element of original array
  while(a>p)    *(a)=*(a-1),a--;
  *a=element;
  return 1;
}

int array_delete(int *a, size_t size, size_t position)
/*Removes the element a[position] from the array. The `size' denotes the  number of
  elements in the array before the removal. Returned zero if the deletion failed
else returns a positive integer.*/
{
  if (position >=size)
    {
      fprintf(stderr,"\narray_delete: The specified position %i is not less than the"
	      " size of the array which is %i\n",position,size);
      return 0;
    }
  int *last=a+size-1;// points to the last element
  a+=position;//a now points to the position of the deltetion
  while(a<last) *(a)=*(a+1),a++;
  return 1;
}

void array_reverse(int *a, size_t size)
/* Reverses the array `a'. The `size' represents the number of elements in `a'*/
{
  int i,t;
  for(i=0; i < size/2 ; i++)
    {
      t=a[i]; a[i]=a[size-i-1]; a[size-i-1]=t;
    }
}

void input_array(int *a, size_t size)
/*Inputs from cin*/
{
  while(size--)
    scanf("%i",a++);
}
  
int main()
{
  const MAX = 20;
  int a[MAX];
 
  printf("With How many numbers do you wanto start with?");
  size_t s;
  scanf("%i", &s);
  printf("Enter the array:");
  input_array(a,s);
  char i;
  do{
    printf("\nWhat do you want to do?"
	   "\n 1. Insert an element.\n 2. Delete an element \n 3. Reverse"
	   "\n 4. Display \n 5. Exit\n");
    
    scanf("%c", &i);
    switch(i)
      {
      case '1':
	{
	  printf("Enter the Position (zero-based) and the element to be inserted:");
	  int e;
	  size_t p;
	  scanf("%i%i",&p,&e);
	  array_insert(a,s,e,p);
	  s++;
	  printf("Done!\n");
	  break;
	}
      case '2':
	{
	  printf("Enter the position at which you want to delete the element:");
	  size_t p;
	  scanf("%i",&p);
	  array_delete(a,s,p);
	  s--;
	  printf("Done!\n");
	  break;
	}
      case '3':
	{
	  array_reverse(a,s);
	  printf("Done!\n");
	  break;
	}
      case '4':
	{
	  printf("\n");
	  array_print(a,s);
	  printf("\n\n");
	  break;
	}
      }
  }while(i!='5');
    /*
	  
  //printf("Size:%i",s);
  array_print(a,s);
  array_insert(a,5,7,3);
  printf("\n");array_print(a,s);
  array_delete(a,6,2);
  printf("\n");array_print(a,s);
  array_reverse(a,5);
  printf("\n");array_print(a,s);
    */
  return 0;
}