Task: Set consolidation
C++: #include <algorithm>
#include <iostream>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;


void SimpleConsolidate(vector<unordered_set<char>>& sets)
{
    
    for(auto last = sets.rbegin(); last != sets.rend(); ++last)
        for(auto other = last + 1; other != sets.rend(); ++other)
        {
            bool hasIntersection = any_of(last->begin(), last->end(), 
                                          [&](auto val)
                                          { return other->contains(val); });
            if(hasIntersection)
            {
                other->merge(*last);
                sets.pop_back();
                break;
            }
        }
}



struct Node
{
    char Value;
    Node* Parent = nullptr;
};    

Node* FindTop(Node& node)
{
    auto top = &node;
    while (top != top->Parent) top = top->Parent;
    for(auto element = &node; element->Parent != top; )
    {
        
        auto parent = element->Parent;
        element->Parent = top;
        element = parent;
    }
    return top;
}

vector<unordered_set<char>> FastConsolidate(const vector<unordered_set<char>>& sets)
{
    unordered_map<char, Node> elements;
    for(auto& set : sets)
    {
        Node* top = nullptr;
        for(auto val : set)
        {
            auto itr = elements.find(val);
            if(itr == elements.end())
            {
                
                auto& ref = elements[val] = Node{val, nullptr};
                if(!top) top = &ref;
                ref.Parent = top;
            }
            else
            {
                auto newTop = FindTop(itr->second);
                if(top)
                {
                    top->Parent = newTop;
                    itr->second.Parent = newTop;
                }
                else
                {
                    top = newTop;
                }
            }
        }
    } 

    unordered_map<char, unordered_set<char>> groupedByTop;
    for(auto& e : elements)
    {
        auto& element = e.second;
        groupedByTop[FindTop(element)->Value].insert(element.Value);
    }

    vector<unordered_set<char>> ret;
    for(auto& itr : groupedByTop)
    {
        ret.push_back(move(itr.second));
    }

    return ret;
}

void PrintSets(const vector<unordered_set<char>>& sets)
{
    for(const auto& set : sets)
    {
        cout << "{ ";
        for(auto value : set){cout << value << " ";}
        cout << "} "; 
    }
    cout << "\n";
}

int main()
{
    const unordered_set<char> AB{'A', 'B'}, CD{'C', 'D'}, DB{'D', 'B'}, 
                              HIJ{'H', 'I', 'K'}, FGH{'F', 'G', 'H'};
                              
    vector <unordered_set<char>> AB_CD {AB, CD};
    vector <unordered_set<char>> AB_DB {AB, DB};
    vector <unordered_set<char>> AB_CD_DB {AB, CD, DB};
    vector <unordered_set<char>> HIJ_AB_CD_DB_FGH {HIJ, AB, CD, DB, FGH};

    PrintSets(FastConsolidate(AB_CD));
    PrintSets(FastConsolidate(AB_DB));
    PrintSets(FastConsolidate(AB_CD_DB));
    PrintSets(FastConsolidate(HIJ_AB_CD_DB_FGH));

    SimpleConsolidate(AB_CD);
    SimpleConsolidate(AB_DB);
    SimpleConsolidate(AB_CD_DB);
    SimpleConsolidate(HIJ_AB_CD_DB_FGH);

    PrintSets(AB_CD);
    PrintSets(AB_DB);
    PrintSets(AB_CD_DB);
    PrintSets(HIJ_AB_CD_DB_FGH);
}

Go: package main

import "fmt"

type set map[string]bool

var testCase = []set{
    set{"H": true, "I": true, "K": true},
    set{"A": true, "B": true},
    set{"C": true, "D": true},
    set{"D": true, "B": true},
    set{"F": true, "G": true, "H": true},
}

func main() {
    fmt.Println(consolidate(testCase))
}

func consolidate(sets []set) []set {
    setlist := []set{}
    for _, s := range sets {
        if s != nil && len(s) > 0 {
            setlist = append(setlist, s)
        }
    }
    for i, s1 := range setlist {
        if len(s1) > 0 {
            for _, s2 := range setlist[i+1:] {
                if s1.disjoint(s2) {
                    continue
                }
                for e := range s1 {
                    s2[e] = true
                    delete(s1, e)
                }
                s1 = s2
            }
        }
    }
    r := []set{}
    for _, s := range setlist {
        if len(s) > 0 {
            r = append(r, s)
        }
    }
    return r
}

func (s1 set) disjoint(s2 set) bool {
    for e := range s2 {
        if s1[e] {
            return false
        }
    }
    return true
}