aoc 2017, days 1-20

1 files changed, 47 insertions, 0 deletions

diff --git a/2017/src/day17.cpp b/2017/src/day17.cpp
new file mode 100644
index 0000000..6cf498b
--- /dev/null
+++ b/2017/src/day17.cpp
@@ -0,0 +1,47 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+void
+part1(size_t steps, size_t iterations)
+{
+        vector<size_t> buffer{ 0 };
+        size_t         pos = 0;
+
+        for ( size_t i = 1; i <= iterations; ++i ) {
+                pos = (pos + steps) % i + 1;
+                buffer.insert(buffer.begin() + static_cast<vector<size_t>::difference_type>(pos), i);
+        }
+
+        cout << "Part1: " << buffer[(pos + 1) % buffer.size()] << '\n';
+}
+
+void
+part2(size_t steps, size_t iterations)
+{
+        size_t pos   = 0;
+        size_t value = 0;
+
+        for ( size_t i = 1; i <= iterations; ++i ) {
+                pos = (pos + steps) % i;
+                if ( pos == 0 ) {
+                        value = i;
+                }
+                pos = (pos + 1) % (i + 1);
+        }
+
+        cout << "Part2: " << value << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        const auto input = 371;
+        part1(input, 2017);
+        part2(input, 50'000'000);
+}