Thread: Pointers and printing distinct elements in array

Code:

 #include <stdio.h>
#include <stdlib.h>
void main() 
{ 
 int *currentPoint, *pointerData, *newPoint;
 int i=0, n=0, j=0, freq=0;
 
 printf("Enter the number of random integers to be generated: ");
 scanf("%d", &n);
 while (n<0)
 {
  printf("Enter the number of random integers to be generated: ");
  scanf("%d", &n);
 }
 //allocate unused space for the array
 pointerData = (int*) calloc (n, sizeof(int));
   
 if (pointerData==NULL)
  exit (1);
 
 //set current point to first value in array
 currentPoint=pointerData;
 for (i=0; i < n; i++)
  //create random array
  *(currentPoint+i) = rand() % 10 + 1;
}

Ive created an array using pointers that lets the user generate a random array of 'n' numbers.

Now I need to output, for example:

10 occurs 4 times
6 occurs 7 times
2 occurs 1 times


Whats the best way to get an output like this because Im completely lost?

I cannot use array indices and the final version should contain no ‘square’ brackets.

Thanks

Well sorting the array makes it easy to count how many of each value there is, since they'll all be adjacent in the array.

> I cannot use array indices and the final version should contain no ‘square’ brackets.
A pointless exercise IMO.
You can just write arr[i] for now to make it all work, then go through at the end turning everything into *(arr+i)

For your 'distinct' elements you need a int-Dictionary with key-type = int and value-type = int like C++/STL map<int,int>.

A simple ANSI C implementation for this map eg:

Code:

typedef struct {
  int (*a)[2],i;
} IntDict;

int cmp(const void*a,const void *b) {
  int i=*(int*)a,j=*(int*)b;
  return (i>j)-(i<j);
  }

void add(IntDict *a,int i) {
  int x[2]={i},*p=bsearch(x,a->a,a->i,sizeof*a->a,cmp);
  if( p )
    p[1]++;
  else
  {
    a->a=realloc(a->a,++a->i*sizeof*a->a);
    memcpy(&a->a[a->i-1],x,sizeof x);
    qsort(a->a,a->i,sizeof*a->a,cmp);
  }
}

int main()
{
  IntDict id={0};

  /* insert all your values here, also duplicates... */
  add(&id,3);add(&id,3);add(&id,3);add(&id,3);
  add(&id,2);add(&id,2);add(&id,2);
  add(&id,1);add(&id,1);
  add(&id,0);

  /* print out the dictionary with keys and values */
  /* your distinct values are the dictionary-keys, here in [][0], values are occurrences in [][1] */
  while( id.i-- )
    printf("%5d %d\n",id.a[id.i][1]+1,id.a[id.i][0]),free(id.a[id.i]);

  free(id.a);
  return 0;
}