Solve 2024 day 8 part 1

2024/day-08/main.cpp

@@ -0,0 +1,79 @@
+#include <iostream>
+#include <map>
+#include <set>
+#include <vector>
+
+using namespace std;
+
+void readInput(vector<string> &antennaMap, map<char, set<pair<int, int>>> &antennas)
+{
+    string line;
+    for (size_t row = 0; getline(cin, line); row++) {
+        for (size_t col = 0; col < line.size(); col++) {
+            char frequency = line[col];
+            if (frequency != '.') {
+                if (antennas.count(frequency)) {
+                    antennas.at(frequency).insert({row, col});
+                } else {
+                    antennas.insert({frequency, {{row, col}}});
+                }
+            }
+        }
+        antennaMap.push_back(line);
+    }
+}
+
+bool isInBounds(pair<int, int> location, const vector<string> &map)
+{
+    return (location.first >= 0 && location.first < map.size())
+           && (location.second >= 0 && location.second < map[0].size());
+}
+
+vector<pair<int, int>> getAntinodes(pair<int, int> antenna1,
+                                    pair<int, int> antenna2,
+                                    const vector<string> &antennaMap)
+{
+    if (antenna1 == antenna2) {
+        return {};
+    }
+
+    pair<int, int> directionVector = {antenna2.first - antenna1.first,
+                                      antenna2.second - antenna1.second};
+
+    pair<int, int> antinode1 = {antenna2.first + directionVector.first,
+                                antenna2.second + directionVector.second};
+    pair<int, int> antinode2 = {antenna1.first - directionVector.first,
+                                antenna1.second - directionVector.second};
+
+    vector<pair<int, int>> antinodes;
+    if (isInBounds(antinode1, antennaMap)) {
+        antinodes.push_back(antinode1);
+    }
+    if (isInBounds(antinode2, antennaMap)) {
+        antinodes.push_back(antinode2);
+    }
+    return antinodes;
+}
+
+int main()
+{
+    vector<string> antennaMap;
+    map<char, set<pair<int, int>>> antennas;
+    readInput(antennaMap, antennas);
+
+    set<pair<int, int>> uniqueAntinodes;
+
+    for (auto antennasWithSameFrequency : antennas) {
+        for (auto antenna1 : antennasWithSameFrequency.second) {
+            for (auto antenna2 : antennasWithSameFrequency.second) {
+                vector<pair<int, int>> foundAntinodes = getAntinodes(antenna1, antenna2, antennaMap);
+                for (pair<int, int> antinode : foundAntinodes) {
+                    uniqueAntinodes.insert(antinode);
+                }
+            }
+        }
+    }
+
+    // Part one
+    cout << "Number of unique antinodes: " << uniqueAntinodes.size() << endl;
+}