1 files changed, 87 insertions, 0 deletions

diff --git a/2018/src/day02.cpp b/2018/src/day02.cpp
new file mode 100644
index 0000000..5dc6c7f
--- /dev/null
+++ b/2018/src/day02.cpp
@@ -0,0 +1,87 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+vector<string>
+read_lines(const filesystem::path& filename)
+{
+        ifstream       file{ filename };
+        vector<string> lines;
+
+        for ( string line; getline(file, line); ) {
+                lines.emplace_back(line);
+        }
+
+        return lines;
+}
+
+void
+part1(const vector<string>& lines)
+{
+        int twos   = 0;
+        int threes = 0;
+        for ( const auto& line: lines ) {
+                map<char, int> foo;
+                for ( const auto chr: line ) {
+                        foo[chr]++;
+                }
+
+                set<int> counts;
+                for ( const auto& [chr, count]: foo ) {
+                        counts.insert(count);
+                }
+
+                if ( counts.contains(2) ) {
+                        ++twos;
+                }
+                if ( counts.contains(3) ) {
+                        ++threes;
+                }
+        }
+        cout << "Part 1: " << twos * threes << '\n';
+}
+
+void
+part2(const vector<string>& lines)
+{
+        for ( size_t i = 0; i != lines.size(); ++i ) {
+                for ( size_t j = i + 1; j != lines.size(); ++j ) {
+                        const auto& lhs = lines.at(i);
+                        const auto& rhs = lines.at(j);
+
+                        if ( lhs.length() != rhs.length() ) {
+                                throw runtime_error("invalid data");
+                        }
+
+                        string result;
+                        for ( size_t k = 0; k != lhs.length(); ++k ) {
+                                if ( lhs[k] == rhs[k] ) {
+                                        result += lhs[k];
+                                }
+                        }
+
+                        if ( result.length() + 1 == lhs.length() ) {
+                                cout << "Part 2: " << result << '\n';
+                                return;
+                        }
+                }
+        }
+}
+
+} // namespace
+
+int
+main()
+{
+        auto lines = read_lines("data/day02.txt");
+        part1(lines);
+        part2(lines);
+}