day 3, advent of code 2022

1 files changed, 105 insertions, 0 deletions

diff --git a/2022/src/day03.cpp b/2022/src/day03.cpp
new file mode 100644
index 0000000..773ccf6
--- /dev/null
+++ b/2022/src/day03.cpp
@@ -0,0 +1,105 @@
+#include <algorithm>
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+using namespace std;
+
+set<char>
+make_unique(string_view str)
+{
+        return { begin(str), end(str) };
+}
+
+map<char, int>
+make_lookup()
+{
+        map<char, int> lookup;
+        for ( int i = 0; i != 26; ++i ) {
+                lookup[char('a' + i)] = i + 1;
+                lookup[char('A' + i)] = i + 27;
+        }
+        return lookup;
+}
+
+vector<tuple<set<char>, set<char>>>
+read_file(string_view filename)
+{
+        fstream                             input{ filename };
+        vector<tuple<set<char>, set<char>>> data;
+
+        for ( string line; getline(input, line); ) {
+                const auto lhs = line.substr(0, line.length() / 2);
+                const auto rhs = line.substr(line.length() / 2);
+                data.emplace_back(make_unique(lhs), make_unique(rhs));
+        }
+
+        return data;
+}
+
+vector<string>
+read_file2(string_view filename)
+{
+        fstream        input{ filename };
+        vector<string> data;
+
+        for ( string line; getline(input, line); ) {
+                data.emplace_back(line);
+        }
+
+        return data;
+}
+
+void
+part1(const vector<tuple<set<char>, set<char>>>& data)
+{
+        auto lookup = make_lookup();
+
+        int sum = 0;
+        for ( const auto& [lhs, rhs]: data ) {
+                string intersection;
+                set_intersection(begin(lhs), end(lhs), begin(rhs), end(rhs), back_inserter(intersection));
+
+                sum += lookup[intersection[0]];
+        }
+        cout << sum << endl;
+}
+
+void
+part2(const vector<string>& data)
+{
+        auto lookup = make_lookup();
+
+        int sum = 0;
+        for ( size_t i = 0; i < data.size(); i += 3 ) {
+                map<char, int> count;
+
+                const array<set<char>, 3> sets = { make_unique(data[i]),
+                                                       make_unique(data[i + 1]),
+                                                       make_unique(data[i + 2]) };
+
+                for ( const auto& set: sets ) {
+                        for ( const auto chr: set ) {
+                                count[chr]++;
+                        }
+                }
+
+                for ( const auto& [key, value]: count ) {
+                        if ( value == 3 ) {
+                                sum += lookup[key];
+                        }
+                }
+        }
+        cout << sum << endl;
+}
+
+int
+main()
+{
+        const auto* const filename = "data/day03.txt";
+        part1(read_file(filename));
+        part2(read_file2(filename));
+}