vector<string> letterCombinations(string digits) {
vector<string> ret, alpha;
if (digits.length() == 0) return ret;
string n2s[10] = {" ","","abc","def","ghi","jkl"
,"mno","pqrs","tuv","wxyz"};
for (auto x : digits) {
alpha.push_back(n2s[x-'0']);
}
cartesianProduct(ret, "", alpha);
return ret;
}
void cartesianProduct(vector<string> &ret, string foo
, vector<string> &alpha) {
int len=foo.length(), size=alpha.size();
if (len >= size) {
ret.push_back(foo); return;
}
string sigma = alpha[len];
for (auto x : sigma) {
string bar=foo; bar.push_back(x);
cartesianProduct(ret, bar, alpha);
}
}
template <typename T> GenericFactor<T>&
GenericFactor<T>::multiply (const GenericFactor<T>& g)
{
if (args_ == g.arguments()) {
// optimization
Globals::logDomain
? params_ += g.params()
: params_ *= g.params();
return *this;
}
unsigned range_prod = 1;
bool share_arguments = false;
const std::vector<T>& g_args = g.arguments();
const Ranges& g_ranges = g.ranges();
const Params& g_params = g.params();
for (size_t i = 0; i < g_args.size(); i++) {
size_t idx = indexOf (g_args[i]);
if (idx == args_.size()) {
range_prod *= g_ranges[i];
args_.push_back (g_args[i]);
ranges_.push_back (g_ranges[i]);
} else {
share_arguments = true;
}
}
if (share_arguments == false) {
// optimization
cartesianProduct (g_params.begin(), g_params.end());
} else {
extend (range_prod);
Params::iterator it = params_.begin();
MapIndexer indexer (args_, ranges_, g_args, g_ranges);
if (Globals::logDomain) {
for (; indexer.valid(); ++it, ++indexer) {
*it += g_params[indexer];
}
} else {
for (; indexer.valid(); ++it, ++indexer) {
*it *= g_params[indexer];
}
}
}
return *this;
}
const std::set<std::pair<T, U>> operator* (const std::set<T>& set1, const std::set<U>& set2)
{
return cartesianProduct(set1, set2);
}
