solution for day 5

1 files changed, 62 insertions, 0 deletions

diff --git a/2020/src/day05.cpp b/2020/src/day05.cpp
new file mode 100644
index 0000000..1f5b797
--- /dev/null
+++ b/2020/src/day05.cpp
@@ -0,0 +1,62 @@
+#include <algorithm>
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <string>
+#include <vector>
+#include <numeric>
+using namespace std;
+
+auto
+read_file(string_view filename)
+{
+        fstream input{ filename };
+        return vector<string>{ istream_iterator<string>{ input }, istream_iterator<string>{} };
+}
+
+auto
+to_int(string_view str)
+{
+        auto result = 0U;
+        for ( auto chr: str ) {
+                result <<= 1U;
+                if ( chr == 'B' || chr == 'R' ) {
+                        result |= 1U;
+                }
+        }
+        return result;
+}
+
+void
+part1(const vector<string>& lines)
+{
+        auto value = 0U;
+        for ( const auto& line: lines ) {
+                value = max(value, to_int(line));
+        }
+        cout << value << endl;
+}
+
+void
+part2(const vector<string>& lines)
+{
+        vector<unsigned int> values;
+        transform(lines.begin(), lines.end(), back_inserter(values), to_int);
+
+        sort(values.begin(), values.end());
+
+        for ( size_t idx = 1; idx != values.size(); ++idx ) {
+                if ( values[idx - 1] != values[idx] - 1 ) {
+                        cout << values[idx] - 1 << endl;
+                        break;
+                }
+        }
+}
+
+int
+main()
+{
+        auto lines = read_file("data/day05.txt");
+        part1(lines);
+        part2(lines);
+}