diff --git a/2022/puzzle-21-01.cc b/2022/puzzle-21-01.cc
new file mode 100644
index 0000000..256eb37
--- /dev/null
+++ b/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;
+}
diff --git a/2022/puzzle-21-02.cc b/2022/puzzle-21-02.cc
new file mode 100644
index 0000000..38533ff
--- /dev/null
+++ b/2022/puzzle-21-02.cc
@@ -0,0 +1,181 @@
+//
+// 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)
+  {
+  }
+
+  static auto human() -> Monkey
+  {
+    Monkey monkey;
+    monkey.value_known_ = false;
+    monkey.op_ = 'h';
+    return monkey;
+  }
+
+  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;
+  case '=':
+    return static_cast<Int>(lhs == rhs ? 1 : 0);
+  default:
+    std::abort();
+  }
+}
+
+auto find_lhs(Int result, char op, Int rhs)
+{
+  switch (op) {
+  case '+':  // result = lhs + rhs -> lhs = result - rhs;
+    return result - rhs;
+  case '-':  // result = lhs - rhs -> lhs = result + rhs;
+    return result + rhs;
+  case '*':  // result = lhs * rhs -> lhs = result / rhs
+    return result / rhs;
+  case '/':  // result = lhs / rhs -> lhs = result * rhs;
+    return result * rhs;
+  case '=':
+    return rhs;
+  default:
+    std::abort();
+  }
+}
+
+auto find_rhs(Int result, Int lhs, char op)
+{
+  switch (op) {
+  case '+':  // result = lhs + rhs -> rhs = result - lhs;
+    return result - lhs;
+  case '-':  // result = lhs - rhs -> rhs = lhs - result;
+    return lhs - result;
+  case '*':  // result = lhs * rhs -> rhs = result / lhs
+    return result / lhs;
+  case '/':  // result = lhs / rhs -> rhs = lhs / result;
+    return lhs / result;
+  case '=':
+    return lhs;
+  default:
+    std::abort();
+  }
+}
+
+auto calculate_up(std::map<std::string, Monkey>& monkies)
+{
+  bool changed{true};
+  while (changed) {
+    changed = false;
+    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;
+      }
+      if (lhs->second.op_ == 'h' || rhs->second.op_ == 'h') {
+        continue;
+      }
+
+      monkey.second.value_ = calculate(lhs->second.value_, monkey.second.op_, rhs->second.value_);
+      monkey.second.value_known_ = true;
+      changed = true;
+    }
+  }
+}
+
+auto find_human_value(std::map<std::string, Monkey>& monkies)
+{
+  auto monkey{monkies.find("root"s)};
+  monkey->second.value_ = 1;
+  monkey->second.value_known_ = true;
+  while (monkey->first != "humn"s) {
+    auto lhs{monkies.find(monkey->second.lhs_)};
+    auto rhs{monkies.find(monkey->second.rhs_)};
+    assert(lhs->second.value_known_ ^ rhs->second.value_known_);
+    if (!lhs->second.value_known_) {
+      lhs->second.value_ = find_lhs(monkey->second.value_, monkey->second.op_, rhs->second.value_);
+      lhs->second.value_known_ = true;
+      monkey = lhs;
+    }
+    if (!rhs->second.value_known_) {
+      rhs->second.value_ = find_rhs(monkey->second.value_, lhs->second.value_, monkey->second.op_);
+      rhs->second.value_known_ = true;
+      monkey = rhs;
+    }
+  }
+}
+
+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) {
+      if (id == "humn"s) {
+        auto [it, success] = monkies.insert({id, Monkey::human()});
+        assert(success);
+      }
+      else {
+        auto [it, success] = monkies.insert({id, Monkey(std::stoll(line.substr(6)))});
+        assert(success);
+      }
+    }
+    else {
+      char const op{(id == "root"s) ? '=' : line[11]};
+      auto [it, success] = monkies.insert({id, Monkey(line.substr(6, 4), op, line.substr(13))});
+      assert(success);
+    }
+  }
+
+  calculate_up(monkies);
+  find_human_value(monkies);
+
+  std::cout << "Human's value: " << monkies["humn"s].value_ << "\n";
+  return EXIT_SUCCESS;
+}