aoc 2018, days 1-11

1 files changed, 101 insertions, 0 deletions

diff --git a/2018/src/day05.cpp b/2018/src/day05.cpp
new file mode 100644
index 0000000..9de484d
--- /dev/null
+++ b/2018/src/day05.cpp
@@ -0,0 +1,101 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+namespace {
+
+string
+read_line(const filesystem::path& filename)
+{
+        ifstream file{ filename };
+        string   line;
+        getline(file, line);
+        return line;
+}
+
+bool
+xorEqual(char lhs, char rhs)
+{
+        return (lhs ^ (1 << 5)) == rhs;
+}
+
+#if 0
+void
+part1(string str)
+{
+        size_t idx = 1;
+        while ( idx < str.length() ) {
+                if ( xorEqual(str[idx - 1], str[idx]) ) {
+                        str.erase(idx - 1, 2);
+                        idx = 1;
+                }
+                else {
+                        ++idx;
+                }
+        }
+
+        cout << "Part 1: " << str.length() << '\n';
+}
+#endif
+
+void
+part1_opti(string_view str)
+{
+        string result;
+
+        for ( const auto chr: str ) {
+                if ( !result.empty() && xorEqual(result.back(), chr) ) {
+                        result.pop_back();
+                }
+                else {
+                        result.push_back(chr);
+                }
+        }
+
+        cout << "Part 1: " << result.length() << '\n';
+}
+
+void
+part2(string_view str)
+{
+        size_t min_length = str.size();
+        for ( auto ch = 'a'; ch != 'z'; ++ch ) {
+                string result;
+
+                for ( const auto chr: str ) {
+                        if ( tolower(chr) == ch ) {
+                                // nichts
+                        }
+                        else if ( !result.empty() && xorEqual(result.back(), chr) ) {
+                                result.pop_back();
+                        }
+                        else {
+                                result.push_back(chr);
+                        }
+                }
+                min_length = min(min_length, result.length());
+        }
+
+        cout << "Part 2: " << min_length << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto line = read_line("data/day05.txt");
+        // part1(line);
+        part1_opti(line);
+        part2(line);
+        /*
+        cout << reduce("aA") << '\n';
+        cout << reduce("abBA") << '\n';
+        cout << reduce("abAB") << '\n';
+        cout << reduce("aabAAB") << '\n';
+        cout << reduce("dabAcCaCBAcCcaDA") << '\n';
+        */
+}