int main(int argc, char **argv)
{
if (argc != 2) {
std::cout << argv[0] << ": wanted-exponent\n";
return 0;
}
int want_exponent = std::stoi(std::string(argv[1]));
std::stack<Chain> queue;
queue.push(Chain());
int binary_exponentiation_count = -1;
int log2w = -1;
std::string s;
for (int j = want_exponent; j != 0; j >>= 1) {
s += std::to_string(j & 1);
binary_exponentiation_count += (j & 1);
binary_exponentiation_count++;
log2w++;
}
binary_exponentiation_count--;
std::reverse(s.begin(), s.end());
std::cout << "Exponent: " << want_exponent << " " << s << "b\n";
int best = binary_exponentiation_count;
while (!queue.empty()) {
// Chain top = queue.front();
Chain top = queue.top();
queue.pop();
// std::cout << top.getCurrentOutput() << " " << top.getChainLength() << "\n";
if (top.getChainLength() <= static_cast<std::size_t>(best)) {
if (top.getCurrentOutput() == want_exponent) {
std::vector<ChainOperation> v = top.getOperations();
best = top.getChainLength();
for (auto op : v) {
std::cout << op << " ";
}
std::cout << " x = x**" << std::setw(4) << std::left << top.getCurrentInput() << " Y = x**" << top.getCurrentOutput() << "\n";
} else {
const int in = top.getCurrentInput();
const int out = top.getCurrentOutput();
const int max = (in > out)?(in):(out);
if (max >= want_exponent) {
continue;
}
// how many squarings would it take
int log2m = -1;
{
unsigned int b = max;
while (b >>= 1) {
log2m++;
}
}
const int steps = (log2w - log2m);
const int totalSteps = top.getChainLength() + steps - 1;
if (totalSteps <= best) {
Chain ii_i = Chain(top);
ii_i.advance(ChainOperation::InputInput_StoreInput);
Chain ii_o = Chain(top);
ii_o.advance(ChainOperation::InputInput_StoreOutput);
Chain io_i = Chain(top);
io_i.advance(ChainOperation::InputOutput_StoreInput);
Chain io_o = Chain(top);
io_o.advance(ChainOperation::InputOutput_StoreOutput);
Chain oo_i = Chain(top);
oo_i.advance(ChainOperation::OutputOutput_StoreInput);
Chain oo_o = Chain(top);
oo_o.advance(ChainOperation::OutputOutput_StoreOutput);
if (ii_i.getCurrentInput() != in || ii_i.getCurrentOutput() != out) {
queue.push(ii_i);
}
if (io_i.getCurrentInput() != in || io_i.getCurrentOutput() != out) {
queue.push(io_i);
}
if (oo_i.getCurrentInput() != in || oo_i.getCurrentOutput() != out) {
queue.push(oo_i);
}
if (ii_o.getCurrentInput() != in || ii_o.getCurrentOutput() != out) {
queue.push(ii_o);
}
if (io_o.getCurrentInput() != in || io_o.getCurrentOutput() != out) {
queue.push(io_o);
}
if (oo_o.getCurrentInput() != in || oo_o.getCurrentOutput() != out) {
queue.push(oo_o);
}
}
}
}
}
std::cout << "Best length is " << best << ", binary exponentiation is " << binary_exponentiation_count << " for exponent " << want_exponent << ".\n";
std::cout << best << '\n';
return 0;
}
