1 files changed, 42 insertions, 5 deletions

diff --git a/2025/src/day01.cpp b/2025/src/day01.cpp
index aa1ea42..2650b3c 100644
--- a/2025/src/day01.cpp
+++ b/2025/src/day01.cpp
@@ -28,8 +28,7 @@ part1(const vector<string>& lines)
         auto pos   = 50;
 
         for ( const auto& line: lines ) {
-                auto value = stoi(line.substr(1));
-                value %= 100;
+                const auto value = stoi(line.substr(1)) % 100;
                 pos += (line[0] == 'L') ? (100 - value) : value;
                 if ( pos % 100 == 0 ) {
                         ++zeros;
@@ -45,9 +44,9 @@ part2(const vector<string>& lines)
         auto pos   = 50;
 
         for ( const auto& line: lines ) {
-                auto value = stoi(line.substr(1));
-                while ( value-- > 0 ) {
-                        pos += (line[0] == 'L') ? 99 : 1;
+                const auto delta = (line[0] == 'L') ? 99 : 1;
+                for ( auto value = stoi(line.substr(1)); value > 0; --value ) {
+                        pos += delta;
                         if ( pos % 100 == 0 ) {
                                 ++zeros;
                         }
@@ -56,6 +55,43 @@ part2(const vector<string>& lines)
         cout << "Part 2: " << zeros << '\n';
 }
 
+void
+part2_opti(const vector<string>& lines)
+{
+        auto zeros = 0;
+        auto pos   = 50;
+
+        auto is_zero = [&pos] {
+                return pos % 100 == 0;
+        };
+
+        for ( const auto& line: lines ) {
+                const auto delta = (line[0] == 'L') ? 99 : 1;
+                auto       value = stoi(line.substr(1));
+
+                if ( !is_zero() ) {
+                        for ( ; value > 0 && !is_zero(); --value ) {
+                                pos += delta;
+                        }
+
+                        if ( is_zero() ) {
+                                ++zeros;
+                        }
+                }
+
+                zeros += value / 100;
+                value %= 100;
+
+                for ( ; value > 0; --value ) {
+                        pos += delta;
+                        if ( is_zero() ) {
+                                ++zeros;
+                        }
+                }
+        }
+        cout << "Part2 (Opti): " << zeros << '\n';
+}
+
 } // namespace
 
 int
@@ -64,4 +100,5 @@ main()
         auto data = read_file("data/day01.txt");
         part1(data);
         part2(data);
+        part2_opti(data);
 }