aoc 2025, day 3, part 1

1 files changed, 50 insertions, 0 deletions

diff --git a/2025/src/day03.cpp b/2025/src/day03.cpp
new file mode 100644
index 0000000..c131255
--- /dev/null
+++ b/2025/src/day03.cpp
@@ -0,0 +1,50 @@
+#include <algorithm>
+#include <cctype>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+vector<vector<long>>
+read_file(const filesystem::path& filename)
+{
+        ifstream             file{ filename };
+        vector<vector<long>> lines;
+
+        for ( string line; getline(file, line); ) {
+                vector<long> numbers;
+                for ( auto chr: line ) {
+                        if ( isdigit(chr) ) {
+                                numbers.emplace_back(chr - '0');
+                        }
+                }
+                lines.emplace_back(std::move(numbers));
+        }
+
+        return lines;
+}
+
+void
+part1(const vector<vector<long>>& lines)
+{
+        long sum = 0;
+        for ( const auto& line: lines ) {
+                auto first  = max_element(line.begin(), prev(line.end()));
+                auto second = max_element(next(first), line.end());
+                sum += *first * 10 + *second;
+        }
+        cout << "Part 1: " << sum << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto lines = read_file("data/day03.txt");
+        part1(lines);
+}