1 files changed, 72 insertions, 0 deletions

diff --git a/2016/src/day09.cpp b/2016/src/day09.cpp
new file mode 100644
index 0000000..e0b0468
--- /dev/null
+++ b/2016/src/day09.cpp
@@ -0,0 +1,72 @@
+#include <fstream>
+#include <iostream>
+
+using namespace std;
+
+string
+read_file(string_view filename)
+{
+        fstream input{ filename };
+        string  line;
+        getline(input, line);
+        return line;
+}
+
+void
+part1(string_view line)
+{
+        size_t len = 0;
+        for ( size_t i = 0; i != line.length(); ) {
+                size_t lhs = 0;
+                size_t rhs = 0;
+
+                if ( sscanf(&line[i], "(%zux%zu)", &lhs, &rhs) == 2 ) {
+                        i = line.find(')', i) + 1 + lhs;
+                        len += lhs * rhs;
+                }
+                else {
+                        ++i;
+                        ++len;
+                }
+        }
+        cout << len << endl;
+}
+
+void
+part2(string_view line)
+{
+        function<size_t(string_view)> part2_rec = [&](string_view line) {
+                size_t len = 0;
+                for ( size_t i = 0; i != line.length(); ) {
+                        size_t lhs = 0;
+                        size_t rhs = 0;
+
+                        if ( sscanf(&line[i], "(%zux%zu)", &lhs, &rhs) == 2 ) {
+                                i = line.find(')', i) + 1;
+                                len += part2_rec({ &line[i], lhs }) * rhs;
+                                i += lhs;
+                        }
+                        else {
+                                ++i;
+                                ++len;
+                        }
+                }
+                return len;
+        };
+
+        cout << part2_rec(line) << endl;
+}
+
+int
+main()
+{
+        auto line = read_file("data/day09.txt");
+        // part1("ADVENT");
+        // part1("A(1x5)BC");
+        // part1("(3x3)XYZ");
+        // part1("A(2x2)BCD(2x2)EFG");
+        // part1("(6x1)(1x3)A");
+        // part1("X(8x2)(3x3)ABCY");
+        part1(line);
+        part2(line);
+}