2020 day8

2 files changed, 34 insertions, 16 deletions

diff --git a/src/2020/day8/aoc.cpp b/src/2020/day8/aoc.cpp
index 830141a..6170215 100644
--- a/src/2020/day8/aoc.cpp
+++ b/src/2020/day8/aoc.cpp
@@ -3,31 +3,49 @@
 
 namespace aoc2020 {
 
-static void run(size_t index, std::vector<code>& cs, int* accumlator) {
-  auto& code = cs[index];
-  if (code.executed == 0) {
-    size_t next = index + 1;
-    if (code.type == acc) {
-      *accumlator += code.value;
+static int run(size_t index, std::vector<code> cs, int* accumlator) {
+  if (index < cs.size()) {
+    auto& code = cs[index];
+    if (code.executed == 0) {
+      size_t next = index + 1;
+      if (code.type == acc) {
+        *accumlator += code.value;
+      }
+      if (code.type == jmp) {
+        next = index + code.value;
+      }
+      code.executed += 1;
+      return run(next, cs, accumlator);
     }
-    if (code.type == jmp) {
-      next = index + code.value;
-    }
-    code.executed += 1;
-    run(next, cs, accumlator);
+    return 1;
   }
+  return 0;
 }
 
-int day8(line_view file) {
+std::pair<int, int> day8(line_view file) {
   std::vector<code> cs;
-  int accumlator = 0;
+  int acc0 = 0;
   per_line(file, [&cs](line_view lv) {
     cs.emplace_back(lv);
     return true;
   });
+  run(0, cs, &acc0);
 
-  run(0, cs, &accumlator);
-  return accumlator;
+  auto reset = [](code& c) {
+    c.type = (code_t)(!(int)c.type);
+  };
+  int acc1 = 0;
+  for(auto& code: cs) {
+    if (code.type != acc) {
+      reset(code);
+      acc1 = 0;
+      if (run(0, cs, &acc1) == 0) {
+        break;
+      }
+      reset(code);
+    }
+  }
+  return {acc0, acc1};
 }
 
 } // namespace aoc2020
diff --git a/src/2020/day8/aoc.h b/src/2020/day8/aoc.h
index ae2b8ee..b39b124 100644
--- a/src/2020/day8/aoc.h
+++ b/src/2020/day8/aoc.h
@@ -44,6 +44,6 @@ struct code {
   }
 };
 
-int day8(line_view);
+std::pair<int, int> day8(line_view);
 
 } // namespace aoc2020