diff --git a/2016/puzzle-16-01.cc b/2016/puzzle-16-01.cc
new file mode 100644
index 0000000..aed9213
--- /dev/null
+++ b/2016/puzzle-16-01.cc
@@ -0,0 +1,58 @@
+//
+// Created by Matthew Gretton-Dann on 06/12/2021.
+//
+
+#include <algorithm>
+#include <iostream>
+#include <string>
+
+auto generate_data(std::string const& s) -> std::string
+{
+  std::string s2;
+  std::string result{s};
+  result.push_back('0');
+  std::reverse_copy(s.begin(), s.end(), std::back_inserter(s2));
+  std::transform(s2.begin(), s2.end(), std::back_inserter(result), [](char c) {
+    if (c == '1') {
+      return '0';
+    }
+    if (c == '0') {
+      return '1';
+    }
+    abort();
+  });
+  return result;
+}
+
+auto checksum(std::string const& s) -> std::string
+{
+  std::string result;
+  for (std::size_t i{0}; i < s.size(); i += 2) {
+    if (s[i] == s[i + 1]) {
+      result.push_back('1');
+    }
+    else {
+      result.push_back('0');
+    }
+  }
+  return result;
+}
+
+auto main() -> int
+{
+  constexpr unsigned len{272};
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Unable to read line\n";
+    return 1;
+  }
+  while (line.size() < len) {
+    line = generate_data(line);
+  }
+  line.resize(len);
+  while (line.size() % 2 == 0) {
+    line = checksum(line);
+  }
+  std::cout << "Checksum " << line << '\n';
+  return 0;
+}
\ No newline at end of file
diff --git a/2016/puzzle-16-02.cc b/2016/puzzle-16-02.cc
new file mode 100644
index 0000000..b7c0618
--- /dev/null
+++ b/2016/puzzle-16-02.cc
@@ -0,0 +1,58 @@
+//
+// Created by Matthew Gretton-Dann on 06/12/2021.
+//
+
+#include <algorithm>
+#include <iostream>
+#include <string>
+
+auto generate_data(std::string const& s) -> std::string
+{
+  std::string s2;
+  std::string result{s};
+  result.push_back('0');
+  std::reverse_copy(s.begin(), s.end(), std::back_inserter(s2));
+  std::transform(s2.begin(), s2.end(), std::back_inserter(result), [](char c) {
+    if (c == '1') {
+      return '0';
+    }
+    if (c == '0') {
+      return '1';
+    }
+    abort();
+  });
+  return result;
+}
+
+auto checksum(std::string const& s) -> std::string
+{
+  std::string result;
+  for (std::size_t i{0}; i < s.size(); i += 2) {
+    if (s[i] == s[i + 1]) {
+      result.push_back('1');
+    }
+    else {
+      result.push_back('0');
+    }
+  }
+  return result;
+}
+
+auto main() -> int
+{
+  constexpr unsigned len{35651584};
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Unable to read line\n";
+    return 1;
+  }
+  while (line.size() < len) {
+    line = generate_data(line);
+  }
+  line.resize(len);
+  while (line.size() % 2 == 0) {
+    line = checksum(line);
+  }
+  std::cout << "Checksum " << line << '\n';
+  return 0;
+}
\ No newline at end of file