Unique hats

solution.cpp

#include <iostream>
#include <vector>
#include <unordered_set>

using namespace std;

template <class T>
void print(vector<T> items) {
    for(T item:items)
        cout << item << " ";
    cout << endl;
}

template <class T>
bool is_unique(vector<T> items) {
    if(items.size() == 0)
        return false;

    unordered_set<T> myset; 
    for(T item:items) 
        myset.insert(item); 
  
    return (items.size() == myset.size()); 
}


void print_unique_hats(vector<vector<int>> &men_hats, int row, int size, vector<int> &collection) {
    // sanity
    if(row == size) 
        return;

    auto hats = men_hats[row];
    for(auto hat:hats) {
        collection.push_back(hat);
        if(collection.size() == size)
        {
            if(is_unique<int>(collection))
                print<int>(collection);
        }
        else {
            print_unique_hats(men_hats, row + 1, size, collection);
        }
        collection.pop_back();
    }

    return;
}

int main() {
    int total_men = 3;
    vector<vector<int>> men_hats({{5, 100, 1}, {2}, {5, 100}});
    vector<int> collection;
    print_unique_hats(men_hats, 0, total_men, collection);
}