From f613310b8a49a218078a7ab689f1a2c9ad478897 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Tue, 14 Jan 2025 17:00:14 +0100
Subject: aoc 2016, days 7

---
 2016/src/day07.cpp | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 2016/src/day07.cpp

(limited to '2016/src/day07.cpp')

diff --git a/2016/src/day07.cpp b/2016/src/day07.cpp
new file mode 100644
index 0000000..faa306f
--- /dev/null
+++ b/2016/src/day07.cpp
@@ -0,0 +1,99 @@
+#include <fstream>
+#include <iostream>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+vector<string>
+read_file(string_view filename)
+{
+	fstream input{ filename };
+
+	vector<string> lines;
+
+	for ( string line; getline(input, line); ) {
+		lines.emplace_back(line);
+	}
+
+	return lines;
+}
+
+void
+part1(const vector<string>& lines)
+{
+	long sum = 0;
+	for ( const auto& line: lines ) {
+		long found_inner = 0;
+		long found_outer = 0;
+
+		bool inner = false;
+		for ( size_t i = 0; i + 3 < line.length(); ++i ) {
+			if ( line[i] == '[' ) {
+				inner = true;
+			}
+			if ( line[i] == ']' ) {
+				inner = false;
+			}
+
+			if ( line[i + 0] == line[i + 3] && line[i + 0] != line[i + 1] && line[i + 1] == line[i + 2] ) {
+				if ( inner ) {
+					++found_inner;
+				}
+				else {
+					++found_outer;
+				}
+			}
+		}
+		sum += (found_inner == 0 && found_outer != 0) ? 1 : 0;
+	}
+	cout << sum << endl;
+}
+
+void
+part2(const vector<string>& lines)
+{
+	long sum = 0;
+	for ( const auto& line: lines ) {
+		set<tuple<char, char>> inners;
+		set<tuple<char, char>> outers;
+
+		bool inner = false;
+		for ( size_t i = 0; i + 2 < line.length(); ++i ) {
+			if ( line[i] == '[' ) {
+				inner = true;
+			}
+			if ( line[i] == ']' ) {
+				inner = false;
+			}
+
+			if ( line[i + 0] == line[i + 2] && line[i + 0] != line[i + 1] ) {
+				if ( inner ) {
+					inners.emplace(line[i + 0], line[i + 1]);
+					if ( outers.contains({ line[i + 1], line[i + 0] }) ) {
+						++sum;
+						break;
+					}
+				}
+				else {
+					outers.emplace(line[i + 0], line[i + 1]);
+					if ( inners.contains({ line[i + 1], line[i + 0] }) ) {
+						++sum;
+						break;
+					}
+				}
+			}
+		}
+	}
+	cout << sum << endl;
+}
+
+int
+main()
+{
+	auto lines = read_file("data/day07.txt");
+	part1(lines);
+	part2(lines);
+}
-- 
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