vector_sampling.cpp

#include <iostream>
#include <vector>
#include <map>
#include <string>
#include <tuple>
#include <iterator>
#include <algorithm>
#include <numeric>
#include <random>
#include <iomanip>

using namespace std;

namespace std {
ostream& operator<<(ostream& os, const pair<int, string>& p)
{
    return os << "(" << p.first << ", " << p.second << ")";
}

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vi)
{
    os << "{ ";
    for (const auto& i: vi)
    {
        os << i << ", ";
    }
    os << "}\n";
    return os;
}
}

int int_generator()
{
    static int i = 0;
    return i++;
}

int main() 
{
    constexpr const size_t data_points = 100000;
    constexpr const size_t sample_points = 100;
    
    constexpr const size_t mean = 10;
    constexpr const size_t dev = 3;
    
    random_device rd;
    mt19937 gen{rd()};
    normal_distribution<> d{mean, dev};
    
    std::vector<int> v;
    v.reserve(data_points);
    generate_n(back_inserter(v), data_points, [&] { return d(gen); });

    std::vector<int> samples;
    samples.reserve(sample_points);
    sample(begin(v), end(v), back_inserter(samples),
        sample_points, mt19937{random_device{}()});
        
    map<int, char> hist;
    for (int i : samples) { ++hist[i]; }
    
    for (const auto& [value, count] : hist)
    {
        cout << setw(2) << value << " "
            << string(count, '*') << '\n';
    }

    return 0;
}