aoc 2024, day4

1 files changed, 99 insertions, 0 deletions

diff --git a/2024/src/day04.cpp b/2024/src/day04.cpp
new file mode 100644
index 0000000..f586afb
--- /dev/null
+++ b/2024/src/day04.cpp
@@ -0,0 +1,99 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <string>
+#include <tuple>
+using namespace std;
+
+map<tuple<size_t, size_t>, char>
+read_file(string_view filename)
+{
+        fstream                          input{ filename };
+        map<tuple<size_t, size_t>, char> data;
+
+        size_t yPos = 0;
+        for ( string line; getline(input, line); ) {
+                for ( size_t xPos = 0; xPos != line.size(); ++xPos ) {
+                        data[{ xPos, yPos }] = line[xPos];
+                }
+                ++yPos;
+        }
+
+        return data;
+}
+
+void
+part1(map<tuple<size_t, size_t>, char> data, size_t size)
+{
+        static const tuple<size_t, size_t> dirs[] = {
+                { -1, -1 },
+                { 0, -1 },
+                { 1, -1 },
+                { 1, 0 },
+                { 1, 1 },
+                { 0, 1 },
+                { -1, 1 },
+                { -1, 0 },
+        };
+        long count = 0;
+        for ( size_t y = 0; y != size; ++y ) {
+                for ( size_t x = 0; x != size; ++x ) {
+                        for ( const auto& [dx, dy]: dirs ) {
+                                if ( data[{ x, y }] == 'X' &&
+                                     data[{ x + 1 * dx, y + 1 * dy }] == 'M' &&
+                                     data[{ x + 2 * dx, y + 2 * dy }] == 'A' &&
+                                     data[{ x + 3 * dx, y + 3 * dy }] == 'S' ) {
+                                        ++count;
+                                }
+                        }
+                }
+        }
+        cout << count << endl;
+}
+
+void
+part2(map<tuple<size_t, size_t>, char> data, size_t size)
+{
+        long count = 0;
+        for ( size_t y = 0; y != size; ++y ) {
+                for ( size_t x = 0; x != size; ++x ) {
+                        if ( data[{ x, y }] == 'A' &&
+                             data[{ x - 1, y - 1 }] == 'M' &&
+                             data[{ x - 1, y + 1 }] == 'M' &&
+                             data[{ x + 1, y - 1 }] == 'S' &&
+                             data[{ x + 1, y + 1 }] == 'S' ) {
+                                ++count;
+                        }
+                        if ( data[{ x, y }] == 'A' &&
+                             data[{ x - 1, y - 1 }] == 'S' &&
+                             data[{ x - 1, y + 1 }] == 'M' &&
+                             data[{ x + 1, y - 1 }] == 'S' &&
+                             data[{ x + 1, y + 1 }] == 'M' ) {
+                                ++count;
+                        }
+                        if ( data[{ x, y }] == 'A' &&
+                             data[{ x - 1, y - 1 }] == 'S' &&
+                             data[{ x - 1, y + 1 }] == 'S' &&
+                             data[{ x + 1, y - 1 }] == 'M' &&
+                             data[{ x + 1, y + 1 }] == 'M' ) {
+                                ++count;
+                        }
+                        if ( data[{ x, y }] == 'A' &&
+                             data[{ x - 1, y - 1 }] == 'M' &&
+                             data[{ x - 1, y + 1 }] == 'S' &&
+                             data[{ x + 1, y - 1 }] == 'M' &&
+                             data[{ x + 1, y + 1 }] == 'S' ) {
+                                ++count;
+                        }
+                }
+        }
+        cout << count << endl;
+}
+
+int
+main()
+{
+        auto data = read_file("data/day04.txt");
+        part1(data, 140);
+        part2(data, 140);
+}