perm_generic_impl.hpp

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//****************************************************************************//
//     Copyright (C) 2016-2024 Florent Hivert <Florent.Hivert@lisn.fr>,       //
//                                                                            //
//  This file is part of HP-Combi <https://github.com/libsemigroups/HPCombi>  //
//                                                                            //
//  HP-Combi is free software: you can redistribute it and/or modify it       //
//  under the terms of the GNU General Public License as published by the     //
//  Free Software Foundation, either version 3 of the License, or             //
//  (at your option) any later version.                                       //
//                                                                            //
//  HP-Combi is distributed in the hope that it will be useful, but WITHOUT   //
//  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or     //
//  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License      //
//  for  more details.                                                        //
//                                                                            //
//  You should have received a copy of the GNU General Public License along   //
//  with HP-Combi. If not, see <https://www.gnu.org/licenses/>.               //
//****************************************************************************//
 
// NOLINT(build/header_guard)

 
namespace HPCombi {
 
template <size_t Size, typename Expo>
PermGeneric<Size, Expo>::PermGeneric(std::initializer_list<Expo> il) {
    HPCOMBI_ASSERT(il.size() <= Size);
    std::copy(il.begin(), il.end(), this->v.begin());
    for (Expo i = il.size(); i < Size; i++)
        this->v[i] = i;
}
 
template <size_t Size, typename Expo>
PermGeneric<Size, Expo>
PermGeneric<Size, Expo>::elementary_transposition(uint64_t i) {
    HPCOMBI_ASSERT(i < Size);
    PermGeneric res{{}};
    res[i] = i + 1;
    res[i + 1] = i;
    return res;
}
 
template <size_t Size, typename Expo>
PermGeneric<Size, Expo> PermGeneric<Size, Expo>::inverse() const {
    PermGeneric res;
    for (uint64_t i = 0; i < Size; i++)
        res[this->v[i]] = i;
    return res;
}
 
template <size_t Size, typename Expo>
PermGeneric<Size, Expo> PermGeneric<Size, Expo>::random() {
    static std::random_device rd;
    static std::mt19937 g(rd());
 
    PermGeneric res{{}};
    std::shuffle(res.v.begin(), res.v.end(), g);
    return res;
}
 
template <size_t Size, typename Expo>
typename PermGeneric<Size, Expo>::vect PermGeneric<Size, Expo>::lehmer() const {
    vect res{};
    for (size_t i = 0; i < Size; i++)
        for (size_t j = i + 1; j < Size; j++)
            if (this->v[i] > this->v[j])
                res[i]++;
    return res;
}
 
template <size_t Size, typename Expo>
uint64_t PermGeneric<Size, Expo>::length() const {
    uint64_t res = 0;
    for (size_t i = 0; i < Size; i++)
        for (size_t j = i + 1; j < Size; j++)
            if (this->v[i] > this->v[j])
                res++;
    return res;
}
 
template <size_t Size, typename Expo>
uint64_t PermGeneric<Size, Expo>::nb_descents() const {
    uint64_t res = 0;
    for (size_t i = 0; i < Size - 1; i++)
        if (this->v[i] > this->v[i + 1])
            res++;
    return res;
}
 
template <size_t Size, typename Expo>
uint64_t PermGeneric<Size, Expo>::nb_cycles() const {
    std::array<bool, Size> b{};
    uint64_t c = 0;
    for (size_t i = 0; i < Size; i++) {
        if (!b[i]) {
            for (size_t j = i; !b[j]; j = this->v[j])
                b[j] = true;
            c++;
        }
    }
    return c;
}
 
template <size_t Size, typename Expo>
bool PermGeneric<Size, Expo>::left_weak_leq(PermGeneric other) const {
    for (size_t i = 0; i < Size; i++) {
        for (size_t j = i + 1; j < Size; j++) {
            if ((this->v[i] > this->v[j]) && (other[i] < other[j]))
                return false;
        }
    }
    return true;
}
 
};  //  namespace HPCombi
 
namespace std {

template <size_t Size, typename Expo>
struct hash<HPCombi::PermGeneric<Size, Expo>> {
    size_t operator()(const HPCombi::PermGeneric<Size, Expo> &ar) const {
        return hash<HPCombi::VectGeneric<Size, Expo>>()(ar);
    }
};
 
}  // namespace std