#include <algorithm>
#include <iostream>
#include <random>
#include <stdexcept>
#include <vector>
/*
Returns k randomly selected elements from the input vector.
Characteristics:
- Selects elements without replacement.
- Each element can appear at most once in the result.
- Works for vectors of any runtime size.
- Uses std::sample (C++17), which is specifically designed
for random sampling from a range.
Complexity:
- O(n), where n is the size of the input vector.
Throws:
- std::invalid_argument if k is larger than the vector size.
*/
std::vector<int> getRandomSample(
const std::vector<int>& values,
std::size_t k)
{
if (k > values.size()) {
throw std::invalid_argument(
"Sample size cannot exceed vector size.");
}
// Random device used to seed the generator.
std::random_device rd;
// Mersenne Twister engine.
std::mt19937 generator(rd());
std::vector<int> result;
result.reserve(k);
std::sample(
values.begin(),
values.end(),
std::back_inserter(result),
k,
generator);
return result;
}
int main()
{
try
{
// Example data.
std::vector<int> numbers{
10, 20, 30, 40, 50,
60, 70, 80, 90, 100
};
std::size_t k = 4;
std::vector<int> sample =
getRandomSample(numbers, k);
std::cout << "Random sample:\n";
for (int value : sample) {
std::cout << value << ' ';
}
std::cout << '\n';
}
catch (const std::exception& ex) {
std::cerr << "Error: "
<< ex.what()
<< '\n';
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
/*
run:
Random sample:
40 60 80 90
*/
