From ea701df2dda12a865e5fe1d17562a13983c2ea69 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Wed, 4 Dec 2024 12:47:56 +0100
Subject: aoc 2024, day4

---
 2024/src/day04.cpp | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 2024/src/day04.cpp

(limited to '2024/src/day04.cpp')

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);
+}
-- 
cgit v1.3