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2023 Day 16 Part 2 optimisation

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We reduce the number of items we put on the list of beams to analyse.
Saving memory allocations list modifications.
This commit is contained in:
Matthew Gretton-Dann
2023-12-16 09:46:46 +00:00
parent a3dc84770a
commit a40aaa9d37
1 changed files with 39 additions and 44 deletions
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83
2023/puzzle-16-02.cc
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@@ -126,52 +126,47 @@ private:
while (!beams.empty()) {
auto beam{beams.front()};
beams.pop_front();
if (!loc_valid(beam.loc_)) { continue; }
// Insert into hash of energised locations. If that fails we've done this before and don't
// need to do it again.
if (auto [it, success] = energised_.insert(beam); !success) { continue; }
switch (grid_[beam.loc_.second][beam.loc_.first]) {
case '.':
break;
case '\\':
if (beam.dir_ == north) { beam.dir_ = west; }
else if (beam.dir_ == east) { beam.dir_ = south; }
else if (beam.dir_ == south) { beam.dir_ = east; }
else if (beam.dir_ == west) { beam.dir_ = north; }
else { std::abort(); }
break;
case '/':
if (beam.dir_ == north) { beam.dir_ = east; }
else if (beam.dir_ == east) { beam.dir_ = north; }
else if (beam.dir_ == south) { beam.dir_ = west; }
else if (beam.dir_ == west) { beam.dir_ = south; }
else { std::abort(); }
break;
case '|':
if (beam.dir_ == east || beam.dir_ == west) {
Beam beam2{beam};
beam2.dir_ = north;
beam2.loc_ = beam2.loc_ + beam2.dir_;
beams.push_back(beam2);
beam.dir_ = south;
while (loc_valid(beam.loc_) && energised_.insert(beam).second) {
switch (grid_[beam.loc_.second][beam.loc_.first]) {
case '.':
break;
case '\\':
if (beam.dir_ == north) { beam.dir_ = west; }
else if (beam.dir_ == east) { beam.dir_ = south; }
else if (beam.dir_ == south) { beam.dir_ = east; }
else if (beam.dir_ == west) { beam.dir_ = north; }
else { std::abort(); }
break;
case '/':
if (beam.dir_ == north) { beam.dir_ = east; }
else if (beam.dir_ == east) { beam.dir_ = north; }
else if (beam.dir_ == south) { beam.dir_ = west; }
else if (beam.dir_ == west) { beam.dir_ = south; }
else { std::abort(); }
break;
case '|':
if (beam.dir_ == east || beam.dir_ == west) {
Beam beam2{beam};
beam2.dir_ = north;
beam2.loc_ = beam2.loc_ + beam2.dir_;
beams.push_back(beam2);
beam.dir_ = south;
}
break;
case '-':
if (beam.dir_ == north || beam.dir_ == south) {
Beam beam2{beam};
beam2.dir_ = east;
beam2.loc_ = beam2.loc_ + beam2.dir_;
beams.push_back(beam2);
beam.dir_ = west;
}
break;
default:
std::abort();
}
break;
case '-':
if (beam.dir_ == north || beam.dir_ == south) {
Beam beam2{beam};
beam2.dir_ = east;
beam2.loc_ = beam2.loc_ + beam2.dir_;
beams.push_back(beam2);
beam.dir_ = west;
}
break;
default:
std::abort();
beam.loc_ = beam.loc_ + beam.dir_;
}
beam.loc_ = beam.loc_ + beam.dir_;
beams.push_back(beam);
}
}