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Fuss with 12

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This commit is contained in:
Eric Mertens 2023-03-27 14:11:40 -07:00
parent de2117327e
commit 0ebaa66b24
1 changed files with 17 additions and 15 deletions
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28
2022/12.cpp
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@ -19,10 +19,13 @@ namespace {
auto Parse(std::istream & in) -> std::tuple<Coord, std::vector<Coord>, Coord, Grid> auto Parse(std::istream & in) -> std::tuple<Coord, std::vector<Coord>, Coord, Grid>
{ {
Coord start1 {}; std::tuple<Coord, std::vector<Coord>, Coord, Grid> result {{},{},{},Grid::Parse(in)};
std::vector<Coord> starts2; // I'd use a structured binding here, but not all current compilers
Coord end {}; // supports capture of the resulting bindings in the lambda below
auto grid = Grid::Parse(in); auto& start1 = std::get<0>(result);
auto& starts2 = std::get<1>(result);
auto& end = std::get<2>(result);
auto& grid = std::get<3>(result);
grid.each([&](Coord c, char v) { grid.each([&](Coord c, char v) {
switch (v) { switch (v) {
@ -32,29 +35,28 @@ auto Parse(std::istream & in) -> std::tuple<Coord, std::vector<Coord>, Coord, Gr
} }
}); });
return {start1, std::move(starts2), end, std::move(grid)}; return result;
} }
auto Solve(std::vector<Coord> starts, Coord end, Grid const& grid) -> std::optional<std::int64_t> auto Solve(std::vector<Coord> starts, Coord end, Grid const& grid) -> std::optional<std::int64_t>
{ {
std::vector<Coord> next_layer; std::vector<Coord> next_layer;
std::set<Coord> seen; std::set<Coord> seen;
std::int64_t counter {1}; std::int64_t counter {};
while (!starts.empty()) { while (!starts.empty()) {
for (auto here : starts) { counter++;
for (auto const& here : starts) {
if (!seen.insert(here).second) continue; if (!seen.insert(here).second) continue;
auto here_height = grid[here]; for (auto const next : {Up(here), Down(here), Left(here), Right(here)}) {
for (auto next : {Up(here), Down(here), Left(here), Right(here)}) { if (grid.contains(next) && grid[next] <= grid[here] + 1) {
if (!grid.contains(next)) continue;
if (grid[next] - 1 > here_height) continue;
if (next == end) { return counter; } if (next == end) { return counter; }
next_layer.push_back(next); next_layer.push_back(next);
} }
} }
counter++; }
starts.clear();
std::swap(starts, next_layer); std::swap(starts, next_layer);
next_layer.clear();
} }
return {}; return {};