how to display item-count pair list in c++? - c++

Question

I have created a simple mode calculator and I am displaying random list - something like this:
12 14 11 10 15 13 16 13 14 14 11 13 16 15 15 15 10 14 13 14 12 13 14 12
The mode value is 6
The mode is 14
. But my problem is I can't get the pair list to show instead of showing the list way - I want to display it this as a item-count pair list :
{2,3}, {4,3}, {5,2}, {3,2}, {1,2}
and the modes are clearly 2 and 4.
can anyone help me solve this issue? thanks for the help.
Here is an image for more details: https://imgur.com/a/FYNcxkv
here is my code:
#include <ctime>
#include <iomanip>
#include <iostream>
#include <string>
#include <random>
using namespace std;
default_random_engine e(static_cast<unsigned>(time(NULL)));
void fill(int a[], int size, int value)
{
for(int i = 0; i < size; i++)
a[i] = value;
}
void randomFill(int a[], int size, int lb, int up)
{
uniform_int_distribution<int> u(lb, up);
for(int i = 0; i < size; i++)
a[i] = u(e);
}
void show(int a1d[], int size)
{
for(int i = 0; i < size; i++)
cout << setw(2) << a1d[i] << ' ';
cout << endl;
}
int count(int a1d[], int size, int value)
{
int vcount = 0;
for(int i = 0; i < size; i++)
if(a1d[i] == value) vcount++;
return vcount;
}
int findLargest(int a1d[], int size)
{
int largest = a1d[0];
for(int i = 1; i < size; i++)
if(a1d[i] > largest) largest = a1d[i];
return largest;
}
/*
the mode of a set of things is that thing that appears the greater number of times in the set
a set may have several modes
*/
int computemodes(int source[], int size, int modes[], int& msize)
{
/*
1. fill the modes array with zeroes
*/
fill(modes, size, 0);
/*
2. store the number of times each source element appears in the modes array.
if an element appears more than once in the source array then its counts appears
more than once the modes array.
source and modes form a parallel array structure
*/
for(int i = 0; i < size; i++)
modes[i] = count(source, size, source[i]);
/*
3. calculate the largest number in the modes array. this number is the number of
times the mode or modes appears in the source array
*/
int modevalue = findLargest(modes, size);
/*
4. assign -1 to the mode array elements that are less than the mode value
now only mode values in the modes array are not equal to -1.
the corresponding elements in the source array are the modes.
*/
for(int i = 0; i < size; i++)
if(modes[i] != modevalue) modes[i] = -1;
/*
5. we use the modes array to identify the source elements that are modes:
any element in the modes array that is not -1 corresponds to a mode in the
source array. if the mode is 1 then every source element is a mode
and no element in the modes array is -1; if the mode is greater than 1 then
a. many modes array entries are -1
b. the number of times a mode appears in the source equals its corresponding modes value
c. the number of modes array entries that are not -1 are the number of times the modes
appear in the source array
the following nested for loop transforms the modes array into an array in which
the first appearance of a mode in the source corresponds to a modes array entry
that is not -1 and subsequent appearances of this mode in the source correspond to
modes array entries that are -1.
*/
for(int i = 0; i < size; i++)
if(modes[i] != -1) //first appearance of the mode in the source
for(int j = i + 1; j < size; j++)
if(source[i] == source[j]) modes[j] = -1;
//subsequent appearances
/*
at this point the usage of the modes array changes.
heretofore, an entry that is not -1 in the modes array is the number of times
a mode appears in the source array. now an entry in the modes array is a mode.
the loop adds modes from the source array to the modes array.
msize serves 2 purposes:
a. it is number of modes copied so far.
b. it is the next free modes array position.
*/
msize = 0;
for (int i = 0; i < size; i++)
if (modes[i] != -1) //first occurrence of a mode in the source
{
modes[msize] = source[i];
msize++;
}
return modevalue;
}
int main()
{
const int size = 24;
int a[size];
int m[size];
randomFill(a, size, 10, 16);
show(a, size);
int msize = 0;
int modevalue = computemodes(a, size, m, msize);
cout << "The mode value is " << modevalue << endl;
if (msize == 1)
cout << "The mode is ";
else
cout << "The modes are ";
show(m, msize);
system("pause");
return 0;
}

Answer 1

You can create your map count with:
template <typename T>
std::map<T, std::size_t> map_count(const std::vector<T>& v)
{
std::map<T, std::size_t> res;
for (const auto& e: v) { res[e]++; }
return res;
}
and from that:
template <typename T>
std::pair<const T, std::size_t> find_mode(const std::map<T, std::size_t>& m)
{
if (m.empty()) {throw std::runtime_error("empty map");}
return *std::max_element(m.begin(),
m.end(),
[](const auto& lhs, const auto& rhs){ return lhs.second < rhs.second; }
);
}
Demo

Answer 2

I would design your code problem something like this:
#include <iostream>
#include <string>
#include <random>
#include <vector>
#include <map>
#include <algorithm> // could be used in your calculate function - algorithm
#include <numeric> // same as above.
class ModeCaclulator {
private:
std::vector<int> generatedNumbers_;
int highestModeCount_;
int highestModeValue;
typedef std::map<int,int> Modes;
Modes allModeCounts_;
public:
ModeCalculator() = default; // default constructor
template<typename T = int> // variadic constructor
ModeCalculator( T&&... t ) : generatedNumbers_{ t... } {
calculateModes();
}
std::vector<int>& getAllNumbers() const { return generatedNumbers_; }
int getHighestModeCount() const { return getHighestModeCount_; }
int getHighestModeValue() const { return getHighestModeValue_; }
Modes getAllModes() const { return allModeCounts_; }
void generateNumbers(int count, int lower, int upper) {
std::random_device rd;
std::mt19937 gen( rd() );
std::uniform_int_distribution<> dis( lower, upper );
for ( int i = 0; i < count; i++ )
generateNumbers_.push_back( dis( gen ) );
}
void calculateModes() {
// This is where you would perform your algorithm
// After doing the proper calculations this is where you would
// save the highestModeValue_ & highestModeCount_ as well as
// populating the vector of maps member.
// In this function you can use local lambdas to find the highest mode count and value.
}
void displayModeInformation() const {
std::cout << Random Values: << '\n';
for ( auto& v : generatedNumbers )
std::cout << v << " ";
std::cout << '\n'
std::cout << "Highest Mode Count: " << highestModeCount_ << '\n';
std::cout << "Highest Mode Value: " << highestModeValue_ << '\n';
std::cout << "\n"
std::cout << "All Mode Count & Value Pairs:\n";
for ( auto& p : allModeCounts_ ) {
std::cout << "{" << p.first << "," << p.second << "}" << " "
}
std::cout << '\n';
}
};
int main() {
ModeCalculator mc;
mc.generateNumbers( 15, 1, 16 );
mc.calculateModes();
mc.displayModeInformation();
// If using variadic constructor
ModeCalculate mc2( 12, 15, 14, 19, 18, 12, 15, 19, 21, 12, 18, 19, 21, 14 );
// no need to call calculateModes() this constructor does that for u
mc2.displayModeInformation();
return 0;
}
This makes the code much more readable, and look how clean main is, and all of the functionality is encapsulated into a single class instead of a handful of floating functions... Internal data is protected or hidden and can only be retrieved through accessor functions. The use of stl containers provides a clean interface instead of the use of C style arrays and also helps to prevent the use of raw pointers, and dynamic memory - via new & delete or new[] & delete[]. It also allows the code to be easier to manage and to debug, and provides a user with a generic reusability.