diff --git a/include/aoc/GardenGroups.hpp b/include/aoc/GardenGroups.hpp
new file mode 100644
index 0000000..b4ad1f1
--- /dev/null
+++ b/include/aoc/GardenGroups.hpp
@@ -0,0 +1,33 @@
+// Solutions to the Advent Of Code 2024.
+// Copyright (C) 2025  Stefan Müller
+//
+// This program is free software: you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#pragma once
+
+#include <stack>
+
+#include <aoc/Grid.hpp>
+#include <aoc/LinesSolver.hpp>
+#include <aoc/Point2.hpp>
+
+class GardenGroups
+    : public LinesSolver
+{
+public:
+    virtual const std::string getPuzzleName() const override;
+    virtual const std::string getInputFileName() const override;
+    virtual void finish() override;
+private:
+    void traverseRegion(Grid<bool>& isVisited, std::stack<Point2>& otherRegionsStack, const Point2& start);
+};
diff --git a/src/GardenGroups.cpp b/src/GardenGroups.cpp
new file mode 100644
index 0000000..44dc3aa
--- /dev/null
+++ b/src/GardenGroups.cpp
@@ -0,0 +1,93 @@
+// Solutions to the Advent Of Code 2024.
+// Copyright (C) 2025  Stefan Müller
+//
+// This program is free software: you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include <aoc/GardenGroups.hpp>
+
+const std::string GardenGroups::getPuzzleName() const
+{
+    return "Day 12: Garden Groups";
+}
+
+const std::string GardenGroups::getInputFileName() const
+{
+    return "garden_groups.txt";
+}
+
+void GardenGroups::finish()
+{
+    Grid<bool> isVisited{ lines.size(), lines[0].size() };
+    isVisited.fill(false);
+
+    std::stack<Point2> otherRegionsStack{};
+    otherRegionsStack.emplace(0, 0);
+    while (!otherRegionsStack.empty())
+    {
+        const Point2 position{ otherRegionsStack.top() };
+        otherRegionsStack.pop();
+        if (!isVisited.cell(position))
+        {
+            traverseRegion(isVisited, otherRegionsStack, position);
+        }
+    }
+}
+
+void GardenGroups::traverseRegion(Grid<bool>& isVisited, std::stack<Point2>& otherRegionsStack, const Point2& start)
+{
+    const char plantType{ getCharAt(start) };
+    long long int area{ 0 };
+    long long int perimeter{ 0 };
+    std::stack<Point2> regionStack{};
+    regionStack.push(start);
+
+    while (!regionStack.empty())
+    {
+        const Point2 position{ regionStack.top() };
+        regionStack.pop();
+        if (!isVisited.cell(position))
+        {
+            isVisited.cell(position) = true;
+            area++;
+
+            for (const Point2& direction : Point2::cardinalDirections)
+            {
+                const Point2 next{ position + direction };
+                if (isInBounds(next))
+                {
+                    if (getCharAt(next) == plantType)
+                    {
+                        if (!isVisited.cell(next))
+                        {
+                            regionStack.push(next);
+                        }
+                    }
+                    else
+                    {
+                        perimeter++;
+                        if (!isVisited.cell(next))
+                        {
+                            otherRegionsStack.push(next);
+                        }
+                    }
+                }
+                else
+                {
+                    perimeter++;
+                }
+            }
+        }
+    }
+
+    part1 += area * perimeter;
+}
diff --git a/src/Program.cpp b/src/Program.cpp
index 8d3f1f1..9e20db1 100644
--- a/src/Program.cpp
+++ b/src/Program.cpp
@@ -32,6 +32,7 @@
 #include <aoc/DiskFragmenter.hpp>
 #include <aoc/HoofIt.hpp>
 #include <aoc/PlutonianPebbles.hpp>
+#include <aoc/GardenGroups.hpp>
 #include <aoc/LanParty.hpp>
 
 void Program::run()
@@ -61,6 +62,7 @@ void Program::runSolvers()
     runSolver<DiskFragmenter>(solverEngine);
     runSolver<HoofIt>(solverEngine);
     runSolver<PlutonianPebbles>(solverEngine);
+    runSolver<GardenGroups>(solverEngine);
     runSolver<LanParty>(solverEngine);
 }
 
diff --git a/tests/src/TestCases.cpp b/tests/src/TestCases.cpp
index 2248abc..b63e40a 100644
--- a/tests/src/TestCases.cpp
+++ b/tests/src/TestCases.cpp
@@ -15,6 +15,9 @@
 
 #include <catch2/catch_test_macros.hpp>
 
+#include <aocTests/TestContext.hpp>
+
+// Solver implementations in day order.
 #include <aoc/HistorianHysteria.hpp>
 #include <aoc/RedNosedReports.hpp>
 #include <aoc/MullItOver.hpp>
@@ -26,8 +29,8 @@
 #include <aoc/DiskFragmenter.hpp>
 #include <aoc/HoofIt.hpp>
 #include <aoc/PlutonianPebbles.hpp>
+#include <aoc/GardenGroups.hpp>
 #include <aoc/LanParty.hpp>
-#include <aocTests/TestContext.hpp>
 
 #define REQUIRE_MESSAGE(cond, msg) if (!(cond)) { INFO(msg); REQUIRE(cond); }
 
@@ -174,6 +177,19 @@ TEST_CASE("[PlutonianPebblesTests]")
     }
 }
 
+TEST_CASE("[GardenGroupsTests]")
+{
+    TestContext test;
+    SECTION("FullData")
+    {
+        test.run(std::make_unique<GardenGroups>(), 1477762, 0, test.getInputPaths());
+    }
+    SECTION("ExampleData")
+    {
+        test.run(std::make_unique<GardenGroups>(), 1930, 0, test.getExampleInputPaths());
+    }
+}
+
 TEST_CASE("[LanPartyTests]")
 {
     TestContext test;