algorithms: std::vector -> absl::Span

ortools/algorithms/find_graph_symmetries_test.cc

@@ -262,8 +262,8 @@ class FindSymmetriesTest : public ::testing::Test {
     return dense_perm;
   }
 
-  std::vector<int> ComposePermutations(const std::vector<int>& p1,
-                                       const std::vector<int>& p2) {
+  std::vector<int> ComposePermutations(absl::Span<const int> p1,
+                                       absl::Span<const int> p2) {
     CHECK_EQ(p1.size(), p2.size());
     std::vector<int> composed(p1.size(), -1);
     for (int i = 0; i < p1.size(); ++i) composed[i] = p1[p2[i]];
@@ -274,7 +274,7 @@ class FindSymmetriesTest : public ::testing::Test {
   // with some basic, non-through EXPECT(..) that check that each generator
   // does make the group grow.
   int ComputePermutationGroupSizeAndVerifyBasicIrreductibility(
-      const std::vector<std::unique_ptr<SparsePermutation>>& generators) {
+      absl::Span<const std::unique_ptr<SparsePermutation>> generators) {
     if (generators.empty()) return 1;  // The identity.
     const int num_nodes = generators[0]->Size();
     // The group only contains the identity at first.
@@ -697,8 +697,7 @@ void AddReverseArcsAndFinalize(Graph* graph) {
   graph->Build();
 }
 
-void SetGraphEdges(const std::vector<std::pair<int, int>>& edges,
-                   Graph* graph) {
+void SetGraphEdges(absl::Span<const std::pair<int, int>> edges, Graph* graph) {
   DCHECK_EQ(graph->num_arcs(), 0);
   for (const auto [from, to] : edges) graph->AddArc(from, to);
   AddReverseArcsAndFinalize(graph);

ortools/algorithms/hungarian.cc

@@ -653,7 +653,7 @@ bool InputContainsNan(absl::Span<const std::vector<double>> input) {
 }
 
 void MinimizeLinearAssignment(
-    const std::vector<std::vector<double>>& cost,
+    absl::Span<const std::vector<double>> cost,
     absl::flat_hash_map<int, int>* direct_assignment,
     absl::flat_hash_map<int, int>* reverse_assignment) {
   if (InputContainsNan(cost)) {

ortools/algorithms/hungarian.h

@@ -47,7 +47,7 @@ namespace operations_research {
 
 // See IMPORTANT NOTE at the top of the file.
 void MinimizeLinearAssignment(
-    const std::vector<std::vector<double>>& cost,
+    absl::Span<const std::vector<double>> cost,
     absl::flat_hash_map<int, int>* direct_assignment,
     absl::flat_hash_map<int, int>* reverse_assignment);