PermutationGenerator.cpp

#include <samchon/library/PermutationGenerator.hpp>

using namespace std;
using namespace samchon::library;

PermutationGenerator::PermutationGenerator(size_t n, size_t r)
    : super(n, r)
{
    size_ = n;
    for (size_t i = n - 1; i > n - r; i--)
        size_ *= i;

    dividerArray.assign(n, NULL);
    for (size_t i = 0; i < n; i++)
        dividerArray[i] = i;
}
auto PermutationGenerator::operator[](size_t x) const -> vector<size_t>
{
    vector<size_t> atoms = this->dividerArray;
    vector<size_t> row(r_, NULL);

    for (size_t i = 0; i < row.size(); i++)
    {
        size_t item = x % atoms.size();
        x = (size_t)floor(x / (double)atoms.size());

        row[i] = atoms[item];
        atoms.erase(atoms.begin() + item);
    }
    return row;
}