From 8c96639ec1f6757570510fc27f1c5fabece35eaf Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sun, 16 Nov 2025 13:23:34 +0100
Subject: aoc 2018, days 1-11

---
 2018/src/day03.cpp | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 2018/src/day03.cpp

(limited to '2018/src/day03.cpp')

diff --git a/2018/src/day03.cpp b/2018/src/day03.cpp
new file mode 100644
index 0000000..bed3acb
--- /dev/null
+++ b/2018/src/day03.cpp
@@ -0,0 +1,95 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <regex>
+#include <set>
+#include <tuple>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+struct Claim {
+	int id;
+	int left;
+	int top;
+	int width;
+	int height;
+};
+
+#if 0
+ostream&
+operator<<(ostream& ostrm, const Claim& claim)
+{
+	ostrm << "id: " << claim.id
+	      << " (" << claim.left << ", " << claim.top << ": " << claim.width << "x" << claim.height;
+	return ostrm;
+}
+#endif
+
+vector<Claim>
+read_file(const filesystem::path& filename)
+{
+	ifstream      file{ filename };
+	vector<Claim> claims;
+
+	regex  pattern(R"#((\d+) @ (\d+),(\d+): (\d+)x(\d+))#");
+	smatch match;
+
+	for ( string line; getline(file, line); ) {
+		if ( !regex_search(line, match, pattern) ) {
+			continue;
+		}
+
+		Claim claim{};
+		claim.id     = stoi(match[1]);
+		claim.left   = stoi(match[2]);
+		claim.top    = stoi(match[3]);
+		claim.width  = stoi(match[4]);
+		claim.height = stoi(match[5]);
+
+		claims.emplace_back(claim);
+	}
+
+	return claims;
+}
+
+void
+solve(const vector<Claim>& claims)
+{
+	map<tuple<int, int>, vector<int>> fabric;
+	set<int>                          allIds;
+
+	for ( const auto& claim: claims ) {
+		for ( int x = claim.left; x < claim.left + claim.width; ++x ) {
+			for ( int y = claim.top; y < claim.top + claim.height; ++y ) {
+				fabric[{ x, y }].emplace_back(claim.id);
+			}
+		}
+		allIds.emplace(claim.id);
+	}
+
+	int overlapCount = 0;
+	for ( const auto& [pos, ids]: fabric ) {
+		if ( ids.size() > 1 ) {
+			++overlapCount;
+			for ( const auto& id: ids ) {
+				allIds.erase(id);
+			}
+		}
+	}
+
+	cout << "Part 1: " << overlapCount << '\n';
+	cout << "Part 2: " << *allIds.begin() << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	auto claims = read_file("data/day03.txt");
+	solve(claims);
+}
-- 
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