# dlib C++ Library - disjoint_subsets_sized.h

    // Copyright (C) 2011  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_DISJOINT_SUBsETS_SIZED_Hh_
    #define DLIB_DISJOINT_SUBsETS_SIZED_Hh_

    #include "disjoint_subsets_sized_abstract.h"
    #include "disjoint_subsets.h"
    #include <vector>
    #include "../algs.h"

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        class disjoint_subsets_sized
        {
        public:

            void clear (
            ) noexcept
            {
                disjoint_subsets_.clear();
                sets_size.clear();
                number_of_sets = 0;
            }

            void set_size (
                unsigned long new_size
            )
            {
                disjoint_subsets_.set_size(new_size);
                sets_size.assign(new_size, 1);
                number_of_sets = new_size;
            }

            size_t size (
            ) const noexcept
            {
                return disjoint_subsets_.size();
            }

            unsigned long find_set (
                unsigned long item
            ) const
            {
                // make sure requires clause is not broken
                DLIB_ASSERT(item < size(),
                    "\t unsigned long disjoint_subsets::find_set()"
                    << "\n\t item must be less than size()"
                    << "\n\t item: " << item
                    << "\n\t size(): " << size()
                    << "\n\t this: " << this
                    );

                return disjoint_subsets_.find_set(item);
            }

            unsigned long merge_sets (
                unsigned long a,
                unsigned long b
            )
            {
                // make sure requires clause is not broken
                DLIB_ASSERT(a != b &&
                            a < size() &&
                            b < size() &&
                            find_set(a) == a &&
                            find_set(b) == b,
                    "\t unsigned long disjoint_subsets::merge_sets(a,b)"
                    << "\n\t invalid arguments were given to this function"
                    << "\n\t a: " << a
                    << "\n\t b: " << b
                    << "\n\t size(): " << size()
                    << "\n\t find_set(a): " << find_set(a)
                    << "\n\t find_set(b): " << find_set(b)
                    << "\n\t this: " << this
                    );

                disjoint_subsets_.merge_sets(a, b);

                if (find_set(a) == a) sets_size[a] += sets_size[b];
                else sets_size[b] += sets_size[a];
                --number_of_sets;

                return find_set(a);
            }

            unsigned long get_number_of_sets (
            ) const noexcept
            {
                return number_of_sets;
            }

            unsigned long get_size_of_set(
                    unsigned long item
            ) const
            {
                // make sure requires clause is not broken
                DLIB_ASSERT(item < size() &&
                            find_set(item) == item,
                            "\t unsigned long disjoint_subsets::get_size_of_set()"
                                    << "\n\t invalid arguments were given to this function"
                                    << "\n\t item: " << item
                                    << "\n\t size(): " << size()
                                    << "\n\t find_set(item): " << find_set(item)
                                    << "\n\t this: " << this
                );

                return sets_size[item];
            }

        private:

            /*
                See the book Introduction to Algorithms by Cormen, Leiserson, Rivest and Stein
                for a discussion of how this algorithm works.
            */

            mutable std::vector<unsigned long> sets_size;
            unsigned long number_of_sets{0};
            disjoint_subsets disjoint_subsets_;

        };

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_DISJOINT_SUBsETS_SIZED_Hh_