solution for day 3

1 files changed, 62 insertions, 0 deletions

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);
+}
+