1 files changed, 27 insertions, 5 deletions
diff --git a/src/2022/day17/aoc.cpp b/src/2022/day17/aoc.cpp
index 538dc8f..d7a1099 100644
--- a/src/2022/day17/aoc.cpp
+++ b/src/2022/day17/aoc.cpp
@@ -16,8 +16,7 @@ char next() {
   static int i{0};
   i %= (moves.length - 1);
   const char* p = moves.line;
-  i++;
-  return *(p + i);
+  return *(p + i++);
 }
 
 void print(const rock17& r) {
@@ -141,20 +140,43 @@ rock17 left(rock17 r) {
   return r;
 }
 
-void merge(rock17& floor, rock17 r) {}
+bool collide(uint8_t r1, uint8_t r2) { return r1 & r2; }
+
+void merge(rock17& floor, rock17 r, int n) {
+  auto m = next();
+  printf("%c %d\n", m, r.type);
+  r = m == '>' ? right(r) : left(r);
+
+  uint8_t rt = floor.rs[floor.rs.size() - 1 - n];
+  uint8_t rh = r.rs[0];
+  if (!collide(rt, rh)) {
+    merge(floor, r, n + 1);
+  } else { // merge from n to last with r
+    size_t m{0};
+    // 1. merge
+    for (size_t i = floor.rs.size() - n; m < r.rs.size() && i < floor.rs.size(); i++) {
+      floor.rs[i] |= r.rs[m];
+      m++;
+    }
+    // 2. push if necessary
+    while (m < r.rs.size()) {
+      floor.rs.push_back(r.rs[m++]);
+    }
+  }
+}
 
 std::pair<int, int> day17(line_view file) {
   moves = file;
   rock17 floor{chamber, {0x7F}};
 
-  int n{10};
+  int n{3};
   for (int i = 0; i < n; i++) {
     rock17 r = make_rock(i);
     auto three{3};
     while (three-- > 0) {
       floor.rs.push_back(0x00);
     }
-    merge(floor, r);
+    merge(floor, r, 0);
   }
 
   print(floor);