Histogram

[vpi764]

a program to create a histogram H of 0 ≤ N ≤ 16 entries. A histogram is a set of values
and the associated frequencies of each of those values. For example, a histogram of colors
might contain the colors “red”, “green”, “blue”, with frequencies of 6, 12 and 5, respectively.
H is represented as a global array of 16 of elements, each a struct or tuple containing a
string and an integer, and has the interface:

• A function init to set each element of H to an empty value and a frequency of 0.

• A function insert(s,n) to insert a new element, made up of a value s and a frequency n, into H. A new element is inserted into an empty position of H. If an element with the value s already exists in H, then no new element is inserted into H and instead the frequency of that (existing) element is increased by n.

• A function find(s) to find an element, given a value s, in H. If that element is found,
then the frequency of that element is returned. Otherwise, a value of -1 is returned.

• A function count to return the number of elements of H that are not empty

[Duthomhas]

Why is this reported?

When I get home later I'll post some help. Histograms are a lot easier than you think. ;-)

[Duthomhas]

So, as you were instructed, a histogram is a count of how many items there are. The fruit bowl will do. You might find that the fruit bowl on the table contains:

    3  apples
    27 grapes
    1  orange

Written as a histogram, you could list it as:

    Apple      3
    Grape      27
    Orange     1

You can even have fruits in your histogram that are not in your bowl:

    Apple      3
    Banana     0
    Grape      27
    Orange     1
    Pear       0

You might think this looks a whole lot like a basic inventory. (Because it is!)


Structure

In C++, a std::unordered_map <string, unsigned> is an excellent way to manage a histogram. However, you have not been given that option. You are asked to use a global array composed of either struct or tuple:

#include <string>

struct element
{
  std::string name;
  unsigned    frequency;
};

constexpr int MAX_ENTRIES = 16;

element histogram[ MAX_ENTRIES ];

#include <string>
#include <tuple>

using element = std::tuple <std::string, unsigned> ;

constexpr int MAX_ENTRIES = 16;

element histogram[ MAX_ENTRIES ];

Either way is just as easy, but as a beginner I recommend the struct way.


Functions

Next you only need to implement the functions given you.

void init();
void insert( const std::string& name, unsigned n );
int find( const std::string& name );
int count();

As a freebie, here is a good way to implement count():

int count()
{
  int n = 0;
  for (int i = 0; i < MAX_ENTRIES; i++)
    if (! histogram[i].name.empty())
      n += 1;
  return n;
}

Usage

Using the histogram is now very easy:

int main()
{
  init();

  insert( "Apple", 1 );  // I don't have to insert them all at once!
  insert( "Banana", 0 );  // An element may appear in the histogram with zero occurrences in the data!
  insert( "Grape", 27);
  insert( "Orange", 1 );
  insert( "Pear", 0 );
  insert( "Apple", 2 );

  int n = find( "Orange" );
  if (n > 0) std::cout << "We have at least one orange!\n";
  else       std::cout << "Sorry, no oranges.\n";
}

Hope this helps.

[dutch]

@Duthomhas,

Firstly, presumably the OP should show some actual work.

Secondly, check out OP's previous posts (under previous username which was just changed yesterday). Troll.