aoc 2025, day 1

3 files changed, 74 insertions, 2 deletions

diff --git a/2025/data/.gitkeep b/2025/data/.gitkeep
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/2025/data/.gitkeep
diff --git a/2025/src/day01.cpp b/2025/src/day01.cpp
new file mode 100644
index 0000000..aa1ea42
--- /dev/null
+++ b/2025/src/day01.cpp
@@ -0,0 +1,67 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+vector<string>
+read_file(const filesystem::path& filename)
+{
+        ifstream       file{ filename };
+        vector<string> lines;
+
+        for ( string line; getline(file, line); ) {
+                lines.emplace_back(line);
+        }
+
+        return lines;
+}
+
+void
+part1(const vector<string>& lines)
+{
+        auto zeros = 0;
+        auto pos   = 50;
+
+        for ( const auto& line: lines ) {
+                auto value = stoi(line.substr(1));
+                value %= 100;
+                pos += (line[0] == 'L') ? (100 - value) : value;
+                if ( pos % 100 == 0 ) {
+                        ++zeros;
+                }
+        }
+        cout << "Part 1: " << zeros << '\n';
+}
+
+void
+part2(const vector<string>& lines)
+{
+        auto zeros = 0;
+        auto pos   = 50;
+
+        for ( const auto& line: lines ) {
+                auto value = stoi(line.substr(1));
+                while ( value-- > 0 ) {
+                        pos += (line[0] == 'L') ? 99 : 1;
+                        if ( pos % 100 == 0 ) {
+                                ++zeros;
+                        }
+                }
+        }
+        cout << "Part 2: " << zeros << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto data = read_file("data/day01.txt");
+        part1(data);
+        part2(data);
+}
diff --git a/makefile b/makefile
index 22a1c4b..634c220 100644
--- a/makefile
+++ b/makefile
@@ -6,7 +6,8 @@ all: $(patsubst 2015/src/%.cpp,2015/bin/%,$(wildcard 2015/src/*.cpp)) \
         $(patsubst 2020/src/%.cpp,2020/bin/%,$(wildcard 2020/src/*.cpp)) \
         $(patsubst 2022/src/%.cpp,2022/bin/%,$(wildcard 2022/src/*.cpp)) \
         $(patsubst 2023/src/%.cpp,2023/bin/%,$(wildcard 2023/src/*.cpp)) \
-        $(patsubst 2024/src/%.cpp,2024/bin/%,$(wildcard 2024/src/*.cpp))
+        $(patsubst 2024/src/%.cpp,2024/bin/%,$(wildcard 2024/src/*.cpp)) \
+        $(patsubst 2025/src/%.cpp,2025/bin/%,$(wildcard 2025/src/*.cpp))
 
 %/bin:
         mkdir -p $@
@@ -57,7 +58,11 @@ all: $(patsubst 2015/src/%.cpp,2015/bin/%,$(wildcard 2015/src/*.cpp)) \
 2024/bin/day13-z3: 2024/src/day13-z3.cpp | 2024/bin
         c++ $(CPPFLAGS) $^ -lz3 -o $@
 
+# 2025
+2025/bin/%: 2025/src/%.cpp | 2025/bin
+        c++ $(CPPFLAGS) $^ -o $@
+
 clean:
-        rm -rf 2015/bin 2016/bin 2017/bin 2020/bin 2022/bin 2023/bin 2024/bin
+        rm -rf 2015/bin 2016/bin 2017/bin 2020/bin 2022/bin 2023/bin 2024/bin 2025/bin
 
 .PHONY: all clean