From fcf4708efd24461ea71e3086d5fbd672d53621d2 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sun, 28 Apr 2024 10:40:25 +0200
Subject: day 3, advent of code 2022

---
 2022/src/day03.cpp | 105 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 2022/src/day03.cpp

(limited to '2022/src/day03.cpp')

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));
+}
-- 
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