ResultType vector_comprehension(const std::vector<T>& in_vec, Function func) {
ResultType result;
result.reserve(in_vec.size());
for (auto& elem : in_vec) {
result.push_back(func(elem));
}
return result;
}
std::vector<std::vector<int>> GetCombinationsIterative(const std::vector<int>& input)
{
typedef std::vector<std::vector<int>> ResultType;
typedef std::vector<int> InputType;
typedef std::vector<std::tuple<int, InputType>> ProblemType;
typedef std::map<int, ProblemType> ProblemListType;
typedef std::queue<InputType> LevelResultsType;
ResultType result;
ProblemListType problemTree;
int currentLevel = input.size();
int startLevel = currentLevel;
problemTree[currentLevel] = ProblemType
{
std::tuple<int, InputType> {0, input}
};
InputType temp = input;
int nodeNr = 1;
while (currentLevel > 2)
{
problemTree[currentLevel - 1] = ProblemType{};
const auto& nodes = problemTree[currentLevel];
for (const auto& node : nodes)
{
temp = std::get<1>(node);
for (const auto& element : temp)
{
std::vector<int> diffSet = temp;
diffSet.erase(std::find(diffSet.begin(), diffSet.end(), element));
problemTree[currentLevel - 1].push_back(std::make_tuple(element, diffSet));
}
}
currentLevel = currentLevel - 1;
}
LevelResultsType resultsCurrentLevel;
LevelResultsType resultsPreviousLevel;
while (currentLevel < startLevel)
{
resultsCurrentLevel = {};
const auto& nodes = problemTree[currentLevel];
int partitionSize = currentLevel == 2 ? 2 : resultsPreviousLevel.size() / nodes.size();
for (const auto& node : nodes)
{
temp = std::get<1>(node);
if (temp.size() == 2)
{
resultsPreviousLevel.push({ temp[0], temp[1] });
resultsPreviousLevel.push({ temp[1], temp[0] });
}
for (int i = 0; i < partitionSize ; ++i)
{
auto& previousLevelResult = resultsPreviousLevel.front();
previousLevelResult.insert(previousLevelResult.begin(), std::get<0>(node));
resultsCurrentLevel.push(resultsPreviousLevel.front());
resultsPreviousLevel.pop();
}
}
resultsPreviousLevel = resultsCurrentLevel;
++currentLevel;
}
while (!resultsCurrentLevel.empty())
{
result.push_back(resultsCurrentLevel.front());
resultsCurrentLevel.pop();
}
return result;
}