diff --git a/2018/puzzle-01-01.cc b/2018/puzzle-01-01.cc
new file mode 100644
index 0000000..cd9cebc
--- /dev/null
+++ b/2018/puzzle-01-01.cc
@@ -0,0 +1,21 @@
+//
+// Created by Matthew Gretton-Dann on 01/12/2021.
+//
+
+#include <cstdlib>
+#include <iostream>
+#include <string>
+
+using Int = std::int64_t;
+
+auto main() -> int
+{
+  Int value{0};
+  std::string line;
+  while (std::getline(std::cin, line)) {
+    Int incr{std::stoll(line)};
+    value += incr;
+  }
+  std::cout << "Frequency: " << value << '\n';
+  return EXIT_SUCCESS;
+}
diff --git a/2018/puzzle-01-02.cc b/2018/puzzle-01-02.cc
new file mode 100644
index 0000000..a379d72
--- /dev/null
+++ b/2018/puzzle-01-02.cc
@@ -0,0 +1,35 @@
+//
+// Created by Matthew Gretton-Dann on 01/12/2021.
+//
+
+#include <cstdlib>
+#include <iostream>
+#include <set>
+#include <string>
+#include <vector>
+
+using Int = std::int64_t;
+
+auto main() -> int
+{
+  Int value{0};
+  std::string line;
+  std::set<Int> freqs;
+  std::vector<Int> input;
+  freqs.insert(0);
+
+  while (std::getline(std::cin, line)) {
+    input.emplace_back(std::stoll(line));
+  }
+
+  while (true) {
+    for (auto incr : input) {
+      value += incr;
+      auto [it, success] = freqs.insert(value);
+      if (!success) {
+        std::cout << "Double frequency seen at: " << value << '\n';
+        return 0;
+      }
+    }
+  }
+}