From d73937c6977a7cb6b2516ba662495ef662fd3fb0 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Thu, 4 Jan 2024 14:15:17 +0100
Subject: solution for day 3

---
 2020/src/day03.cpp | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 2020/src/day03.cpp

(limited to '2020/src')

diff --git a/2020/src/day03.cpp b/2020/src/day03.cpp
new file mode 100644
index 0000000..f9cf200
--- /dev/null
+++ b/2020/src/day03.cpp
@@ -0,0 +1,62 @@
+#include <fstream>
+#include <functional>
+#include <iostream>
+#include <iterator>
+#include <numeric>
+#include <string>
+#include <vector>
+using namespace std;
+
+auto
+read_file(string_view filename)
+{
+	fstream        input{ filename };
+	vector<string> data;
+
+	for ( string line; getline(input, line); ) {
+		data.emplace_back(line);
+	}
+
+	return data;
+}
+
+auto
+solve(const vector<string>& puzzle, size_t delta_col, size_t delta_row)
+{
+	size_t col = 0;
+	size_t row = 0;
+
+	auto sum = 0L;
+	while ( row < puzzle.size() ) {
+		if ( puzzle[row][col] == '#' ) {
+			++sum;
+		}
+
+		row += delta_row;
+
+		col += delta_col;
+		col %= puzzle[0].size();
+	}
+	return sum;
+}
+
+void
+part1(const vector<string>& puzzle)
+{
+	cout << solve(puzzle, 3, 1) << endl;
+}
+
+void
+part2(const vector<string>& puzzle)
+{
+	cout << solve(puzzle, 1, 1) * solve(puzzle, 3, 1) * solve(puzzle, 5, 1) * solve(puzzle, 7, 1) * solve(puzzle, 1, 2) << endl;
+}
+
+int
+main()
+{
+	const auto puzzle = read_file("data/day03.txt");
+	part1(puzzle);
+	part2(puzzle);
+}
+
-- 
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