Add solutions for 2022 day 21

2022/puzzle-21-01.cc

@@ -0,0 +1,95 @@
+//
+// Created by Matthew Gretton-Dann on 16/12/2022.
+//
+
+#include <array>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <stdexcept>
+#include <utility>
+
+using Int = std::int64_t;
+using UInt = std::uint64_t;
+using Ints = std::vector<std::pair<Int, Int>>;
+
+using namespace std::string_literals;
+
+struct Monkey
+{
+  Monkey() = default;
+
+  explicit Monkey(Int value) : value_(value), value_known_(true) {}
+
+  Monkey(std::string lhs, char op, std::string rhs)
+      : lhs_(std::move(lhs)), rhs_(std::move(rhs)), op_(op)
+  {
+  }
+
+  Monkey(Monkey const&) = default;
+  Monkey(Monkey&&) = default;
+  auto operator=(Monkey const&) -> Monkey& = default;
+  auto operator=(Monkey&&) -> Monkey& = default;
+  ~Monkey() = default;
+
+  Int value_{0};
+  bool value_known_{false};
+  std::string lhs_;
+  std::string rhs_;
+  char op_{'\0'};
+};
+
+auto calculate(Int lhs, char op, Int rhs)
+{
+  switch (op) {
+  case '+':
+    return lhs + rhs;
+  case '-':
+    return lhs - rhs;
+  case '*':
+    return lhs * rhs;
+  case '/':
+    return lhs / rhs;
+  default:
+    std::abort();
+  }
+}
+
+auto main() -> int
+{
+  std::string line;
+  std::map<std::string, Monkey> monkies;
+
+  while (std::getline(std::cin, line)) {
+    std::string const id(line.substr(0, 4));
+    if (std::isdigit(line[6]) != 0) {
+      auto [it, success] = monkies.insert({id, Monkey(std::stoll(line.substr(6)))});
+      assert(success);
+    }
+    else {
+      auto [it, success] =
+        monkies.insert({id, Monkey(line.substr(6, 4), line[11], line.substr(13))});
+      assert(success);
+    }
+  }
+
+  while (!monkies["root"s].value_known_) {
+    for (auto& monkey : monkies) {
+      if (monkey.second.value_known_) {
+        continue;
+      }
+
+      auto lhs = monkies.find(monkey.second.lhs_);
+      auto rhs = monkies.find(monkey.second.rhs_);
+      if (!lhs->second.value_known_ || !rhs->second.value_known_) {
+        continue;
+      }
+
+      monkey.second.value_ = calculate(lhs->second.value_, monkey.second.op_, rhs->second.value_);
+      monkey.second.value_known_ = true;
+    }
+  }
+
+  std::cout << "Root's value: " << monkies["root"s].value_ << "\n";
+  return EXIT_SUCCESS;
+}