2023 graph: allow multiple sources in tarjan_scc()

yut23 · Feb 21, 2024 · 56c3ebc · 56c3ebc
1 parent 2875b4d
commit 56c3ebc
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Showing 3 changed files with 48 additions and 30 deletions.
diff --git a/2023/src/day20.hpp b/2023/src/day20.hpp
@@ -9,21 +9,22 @@
 #define DAY20_HPP_QRITMDTC
 
 #include "graph_traversal.hpp"
-#include "lib.hpp"       // for DEBUG
-#include <algorithm>     // for all_of, transform, lower_bound, sort
-#include <cassert>       // for assert
-#include <cstddef>       // for size_t
-#include <iostream>      // for istream, ostream, cerr, cout
-#include <iterator>      // for back_inserter, distance
-#include <memory>        // for unique_ptr, make_unique
-#include <numeric>       // for lcm
-#include <queue>         // for queue
-#include <set>           // for set (tarjan_scc)
-#include <sstream>       // for istringstream
-#include <string>        // for string, getline
-#include <unordered_map> // for unordered_map
-#include <utility>       // for move, forward
-#include <vector>        // for vector
+#include "lib.hpp"          // for DEBUG
+#include <algorithm>        // for all_of, transform, lower_bound, sort
+#include <cassert>          // for assert
+#include <cstddef>          // for size_t
+#include <initializer_list> // for initializer_list (single-source tarjan_scc)
+#include <iostream>         // for istream, ostream, cerr, cout
+#include <iterator>         // for back_inserter, distance
+#include <memory>           // for unique_ptr, make_unique
+#include <numeric>          // for lcm
+#include <queue>            // for queue
+#include <set>              // for set (tarjan_scc)
+#include <sstream>          // for istringstream
+#include <string>           // for string, getline
+#include <unordered_map>    // for unordered_map
+#include <utility>          // for move, forward
+#include <vector>           // for vector
 // IWYU pragma: no_include <functional>  // for hash (unordered_map)
 
 namespace aoc::day20 {

diff --git a/2023/src/graph_traversal.hpp b/2023/src/graph_traversal.hpp
@@ -16,12 +16,13 @@
 #include <cassert>           // for assert
 #include <concepts>          // for same_as, integral
 #include <functional>        // for function, greater
-#include <map>               // for map
-#include <queue>             // for priority_queue
-#include <set>               // for set
-#include <stack>             // for stack
-#include <stdexcept>         // for invalid_argument
-#include <tuple>             // for tuple
+#include <initializer_list> // for initializer_list
+#include <map>              // for map
+#include <queue>            // for priority_queue
+#include <set>              // for set
+#include <stack>            // for stack
+#include <stdexcept>        // for invalid_argument
+#include <tuple>            // for tuple
 #include <type_traits> // for conditional_t, invoke_result_t // IWYU pragma: export
 #include <unordered_map> // for unordered_map
 #include <unordered_set> // for unordered_set
@@ -295,9 +296,11 @@ struct tarjan_entry {
  * Components are returned in topological order, along with a set of the
  * directed edges between the components.
  */
-template <class Key, detail::GetNeighbors<Key> GetNeighbors>
+template <class Key,
+          util::concepts::any_iterable_collection<Key> SourceCollection,
+          detail::GetNeighbors<Key> GetNeighbors>
 std::pair<std::vector<std::vector<Key>>, std::set<std::pair<int, int>>>
-tarjan_scc(const Key &source, GetNeighbors &&get_neighbors) {
+tarjan_scc(const SourceCollection &sources, GetNeighbors &&get_neighbors) {
     int index = 0;
     std::stack<Key> S{};
     std::vector<std::vector<Key>> components{};
@@ -355,7 +358,11 @@ tarjan_scc(const Key &source, GetNeighbors &&get_neighbors) {
         return v_entry;
     };
 
-    strongconnect(source, strongconnect);
+    for (const auto &source : sources) {
+        if (!entries.contains(source)) {
+            strongconnect(source, strongconnect);
+        }
+    }
 
     // check edges
     if constexpr (aoc::DEBUG) {
@@ -382,6 +389,13 @@ tarjan_scc(const Key &source, GetNeighbors &&get_neighbors) {
     return {std::move(components), std::move(reversed_links)};
 }
 
+template <class Key, detail::GetNeighbors<Key> GetNeighbors>
+std::pair<std::vector<std::vector<Key>>, std::set<std::pair<int, int>>>
+tarjan_scc(const Key &source, GetNeighbors &&get_neighbors) {
+    const std::initializer_list<Key> sources = {source};
+    return tarjan_scc<Key>(sources, get_neighbors);
+}
+
 /**
  * Longest path algorithm for a DAG.
  */
@@ -699,6 +713,8 @@ void _lint_helper_template(
     topo_sort(source, get_neighbors);
 
     tarjan_scc(source, get_neighbors);
+    const std::vector<Key> sources{source, source};
+    tarjan_scc<Key>(sources, get_neighbors);
 
     longest_path_dag(source, get_neighbors, get_distance, is_target);
 

diff --git a/2023/src/test00_graph.cpp b/2023/src/test00_graph.cpp
@@ -9,12 +9,13 @@
 #include "unit_test/unit_test.hpp"
 
 #include "graph_traversal.hpp"
-#include <algorithm>     // for sort
-#include <cstddef>       // for size_t
-#include <set>           // for set
-#include <unordered_map> // for unordered_map
-#include <utility>       // for pair
-#include <vector>        // for vector
+#include <algorithm>        // for sort
+#include <cstddef>          // for size_t
+#include <initializer_list> // for initializer_list (single-source tarjan_scc)
+#include <set>              // for set
+#include <unordered_map>    // for unordered_map
+#include <utility>          // for pair
+#include <vector>           // for vector
 
 namespace aoc::graph::test {