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Speed up day 18 part 2.

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Bert Peters
2019-12-23 23:48:53 +01:00
parent 8bbd9705a6
commit 3da0605201
1 changed files with 4 additions and 8 deletions
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12
2019/src/day18.cpp
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@@ -155,7 +155,7 @@ void aoc2019::day18_part1(std::istream &input, std::ostream &output) {
}
void aoc2019::day18_part2(std::istream &input, std::ostream &output) {
using state_t = std::tuple<unsigned int, std::array<char, 4>>;
using state_t = std::pair<unsigned int, std::array<char, 4>>;
auto map = read_map(input);
@@ -177,7 +177,7 @@ void aoc2019::day18_part2(std::istream &input, std::ostream &output) {
const auto implied_graph = compute_implied_graph(map);
std::priority_queue<std::pair<int, state_t>, std::vector<std::pair<int, state_t>>, std::greater<>> todo;
std::map<state_t, int> visited;
std::map<std::pair<unsigned int, char>, int> visited;
todo.emplace(0, state_t(0, {'@', '*', '^', '/'}));
auto target_size = std::count_if(implied_graph.cbegin(), implied_graph.cend(),
@@ -188,10 +188,6 @@ void aoc2019::day18_part2(std::istream &input, std::ostream &output) {
const auto[dist, state] = todo.top();
todo.pop();
if (visited[state] < dist) {
continue;
}
auto[keys, pos] = state;
if (std::__popcount(keys) == target_size) {
@@ -217,8 +213,8 @@ void aoc2019::day18_part2(std::istream &input, std::ostream &output) {
next_pos[i] = edge.first;
state_t next_state = {next_keys, next_pos};
if (auto it = visited.find(next_state); it == visited.end() || it->second > next_dist) {
visited[next_state] = next_dist;
if (auto it = visited.find({next_keys, next_pos[i]}); it == visited.end() || it->second > next_dist) {
visited[{next_keys, next_pos[i]}] = next_dist;
todo.emplace(next_dist, next_state);
}
}