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Make topological sort generic.

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Bert Peters
2019-12-14 15:52:55 +01:00
parent 17a37ccf5a
commit a655436ac6
2 changed files with 46 additions and 23 deletions
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26
2019/src/day14.cpp
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@@ -7,6 +7,7 @@
#include <regex>
#include <charconv>
#include "days.hpp"
#include "utils.hpp"
namespace {
typedef std::pair<std::string, std::int64_t> requirement_t;
@@ -68,7 +69,7 @@ namespace {
std::vector<std::string> topological_order(const std::map<reqlist_t, reqlist_t> &recipes) {
std::vector<std::string> order;
std::unordered_map<std::string_view, std::vector<std::string>> edges;
std::unordered_map<std::string, std::vector<std::string>> edges;
for (auto &entry : recipes) {
for (auto &production : entry.first) {
std::transform(entry.second.begin(), entry.second.end(), std::back_inserter(edges[production.first]),
@@ -78,28 +79,7 @@ namespace {
}
}
std::unordered_map<std::string_view, int> incoming_edge_count;
for (const auto &entry : edges) {
for (const auto &parent : entry.second) {
incoming_edge_count[parent]++;
}
}
std::deque<std::string_view> childless{"FUEL"};
while (!childless.empty()) {
auto current = childless.front();
childless.pop_front();
order.emplace_back(current);
for (const auto &parent : edges[current]) {
if (--incoming_edge_count[parent] == 0) {
childless.push_back(parent);
}
}
}
return order;
return aoc2019::topological_sort(edges);
}
std::int64_t ore_to_fuel(const std::map<reqlist_t, reqlist_t> &recipes, std::int64_t amount = 1) {

43
2019/src/utils.hpp
View File

@@ -27,6 +27,49 @@ namespace aoc2019 {
std::vector<int> run_intcode(std::vector<int> &program, std::deque<int> inputs = {});
template<class Node>
std::vector<Node> topological_sort(const std::unordered_map<Node, std::vector<Node>> &edge_list) {
std::unordered_map<Node, int> incoming_edges;
for (auto &entry : edge_list) {
// Ensure entry for parent exist
incoming_edges[entry.first] += 0;
for (auto &node : entry.second) {
incoming_edges[node]++;
}
}
std::vector<Node> order;
std::deque<Node> childless;
for (auto &entry : incoming_edges) {
if (!entry.second) {
childless.push_back(entry.first);
}
}
while (!childless.empty()) {
auto current = childless.front();
childless.pop_front();
order.emplace_back(current);
if (auto it = edge_list.find(current); it != edge_list.end()) {
for (const auto &parent : it->second) {
if (--incoming_edges[parent] == 0) {
childless.push_back(parent);
}
}
}
}
if (order.size() != incoming_edges.size()) {
throw std::domain_error("Not a DAG.");
}
return order;
}
class IntCodeComputer {
public:
typedef std::int64_t value_t;