Add solution for "Day 8: Resonant Collinearity", part 1

src/Point2.cpp

@@ -47,6 +47,11 @@ bool Point2::operator!=(const Point2& rhs) const
     return !(*this == rhs);
 }
 
+bool Point2::operator<(const Point2& rhs) const
+{
+    return x < rhs.x || (x == rhs.x && y < rhs.y);
+}
+
 Point2 Point2::operator+(const Point2& rhs) const
 {
     return Point2(x + rhs.x, y + rhs.y);

src/Program.cpp

@@ -28,6 +28,7 @@
 #include <aoc/PrintQueue.hpp>
 #include <aoc/GuardGallivant.hpp>
 #include <aoc/BridgeRepair.hpp>
+#include <aoc/ResonantCollinearity.hpp>
 #include <aoc/HoofIt.hpp>
 #include <aoc/PlutonianPebbles.hpp>
 #include <aoc/LanParty.hpp>
@@ -55,6 +56,7 @@ void Program::runSolvers()
     runSolver<PrintQueue>(solverEngine);
     runSolver<GuardGallivant>(solverEngine);
     runSolver<BridgeRepair>(solverEngine);
+    runSolver<ResonantCollinearity>(solverEngine);
     runSolver<HoofIt>(solverEngine);
     runSolver<PlutonianPebbles>(solverEngine);
     runSolver<LanParty>(solverEngine);

src/ResonantCollinearity.cpp

@@ -0,0 +1,72 @@
+// 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/ResonantCollinearity.hpp>
+
+#include <iostream>
+
+const std::string ResonantCollinearity::getPuzzleName() const
+{
+    return "Day 8: Resonant Collinearity";
+}
+
+const std::string ResonantCollinearity::getInputFileName() const
+{
+    return "resonant_collinearity.txt";
+}
+
+void ResonantCollinearity::finish()
+{
+    for (int j = 0; j < lines.size(); j++)
+    {
+        for (int i = 0; i < lines[j].size(); i++)
+        {
+            if (lines[j][i] != getEmptyChar())
+            {
+                addNewAntenna({ i, j });
+            }
+        }
+    }
+
+    part1 = antinodes_.size();
+}
+
+constexpr char ResonantCollinearity::getEmptyChar()
+{
+    return '.';
+}
+
+void ResonantCollinearity::addNewAntenna(Point2&& newPosition)
+{
+    const auto [it, success] = antennas_.insert({ getPosition(newPosition), { newPosition } });
+    if (!success)
+    {
+        for (const auto& oldPosition : it->second)
+        {
+            addNewAntinode(newPosition * 2 - oldPosition);
+            addNewAntinode(oldPosition * 2 - newPosition);
+        }
+
+        it->second.push_back(newPosition);
+    }
+}
+
+void ResonantCollinearity::addNewAntinode(Point2&& newPosition)
+{
+    if (isInBounds(newPosition))
+    {
+        antinodes_.insert(newPosition);
+    }
+}