1 files changed, 54 insertions, 1 deletions
diff --git a/src/2018/day7/aoc.h b/src/2018/day7/aoc.h
index bd2634a..25d127d 100644
--- a/src/2018/day7/aoc.h
+++ b/src/2018/day7/aoc.h
@@ -1,5 +1,58 @@
 #pragma once
 #include "common.h"
+#include <map>
+#include <set>
 
 namespace aoc2018 {
-}
+
+struct instruction {
+  static std::map<char, instruction*> instructions;
+
+  static instruction* make(char x) {
+    auto it = instructions.find(x);
+    if (it == instructions.end()) {
+      auto p = instructions.insert({x, new instruction{x, false, {}}});
+      return p.first->second;
+    }
+    return it->second;
+  }
+
+  static instruction* next() {
+    instruction* n = nullptr;
+    for (auto& kv : instructions) {
+      if (kv.second->ready()) {
+        if (n == nullptr) {
+          n = kv.second;
+        } else {
+          if (*kv.second < *n) {
+            n = kv.second;
+          }
+        }
+      }
+    }
+    return n; // if nullptr all done
+  }
+
+  char label;
+  bool done;
+  std::set<instruction*> deps;
+
+  void add_dependency(instruction* x) noexcept { deps.insert(x); }
+  void make_done() noexcept { done = true; }
+  bool operator<(const instruction& other) const noexcept { return label < other.label; }
+
+  bool ready(const std::set<instruction*> ds) const noexcept {
+    for (auto& i : ds) {
+      if (!i->done) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  bool ready() const noexcept { return !done && (deps.empty() || ready(deps)); }
+};
+
+void day7(line_view, char[]);
+
+} // namespace aoc2018