aoc 2024, day 20, cleanup

1 files changed, 14 insertions, 14 deletions

diff --git a/2024/src/day20.cpp b/2024/src/day20.cpp
index 3e79f33..091c2ab 100644
--- a/2024/src/day20.cpp
+++ b/2024/src/day20.cpp
@@ -45,8 +45,6 @@ bfs(const tuple<pos_type, pos_type, set<pos_type>>& data)
 
         map<pos_type, long> path;
 
-        set<pos_type> seen;
-
         queue<tuple<pos_type, long>> queue;
         queue.push({ start, 0 });
 
@@ -54,11 +52,9 @@ bfs(const tuple<pos_type, pos_type, set<pos_type>>& data)
                 auto [pos, dist] = queue.front();
                 queue.pop();
 
-                if ( seen.contains(pos) ) {
+                if ( path.contains(pos) ) {
                         continue;
                 }
-                seen.insert(pos);
-
                 path[pos] = dist;
 
                 if ( pos == end ) {
@@ -67,10 +63,9 @@ bfs(const tuple<pos_type, pos_type, set<pos_type>>& data)
 
                 auto [x, y] = pos;
                 for ( const auto& new_pos: vector<pos_type>{ { x - 1, y }, { x, y - 1 }, { x + 1, y }, { x, y + 1 } } ) {
-                        if ( walls.contains(new_pos) ) {
-                                continue;
+                        if ( !walls.contains(new_pos) ) {
+                                queue.push({ new_pos, dist + 1 });
                         }
-                        queue.push({ new_pos, dist + 1 });
                 }
         }
         return path;
@@ -92,7 +87,7 @@ part1(const tuple<pos_type, pos_type, set<pos_type>>& data)
                                 continue;
                         }
                         pos_type new_pos{ x + 2 * dx, y + 2 * dy };
-                        if ( path.contains(new_pos) && dist < path.at(new_pos) && path.at(new_pos) - dist >= 100 + 2 ) {
+                        if ( path.contains(new_pos) && path.at(new_pos) - dist >= 100 + 2 ) {
                                 ++count;
                         }
                 }
@@ -110,15 +105,20 @@ part2(const tuple<pos_type, pos_type, set<pos_type>>& data)
                 auto [x, y] = pos;
 
                 for ( size_t r = 2; r != 21; ++r ) {
+                        set<pos_type> candidates;
                         for ( size_t dx = 0; dx != r + 1; ++dx ) {
                                 size_t dy = r - dx;
 
-                                for ( const auto& new_pos: set<pos_type>{ { x + dx, y + dy }, { x - dx, y + dy }, { x + dx, y - dy }, { x - dx, y - dy } } ) {
-                                        if ( path.contains(new_pos) && dist < path.at(new_pos) && path.at(new_pos) - dist >= 100 + long(r) ) {
-                                                ++count;
-                                        }
-                                }
+                                candidates.insert({ x + dx, y + dy });
+                                candidates.insert({ x - dx, y + dy });
+                                candidates.insert({ x + dx, y - dy });
+                                candidates.insert({ x - dx, y - dy });
                         }
+
+                        auto temp_dist = dist;
+                        count += ranges::count_if(candidates, [&](const auto& new_pos) {
+                                return path.contains(new_pos) && path.at(new_pos) - temp_dist >= 100 + long(r);
+                        });
                 }
         }
         cout << count << endl;