Add day 2 of 2021's puzzles.

2021/puzzle-02-01.cc

@@ -0,0 +1,32 @@
+//
+// Created by Matthew Gretton-Dann on 02/12/2021.
+//
+
+#include <string>
+#include <iostream>
+
+int main()
+{
+    using namespace std::string_literals;
+
+    static const auto fwd{"forward "s};
+    static const auto down{"down "s};
+    static const auto up{"up "s};
+
+    std::string line;
+    unsigned long horiz{0};
+    unsigned long depth{0};
+    while (std::getline(std::cin, line)) {
+        if (line.size() > fwd.size() && line.substr(0,fwd.size()) == fwd) {
+            horiz += std::stoul(line.substr(fwd.size()));
+        }
+        if (line.size() > down.size() && line.substr(0,down.size()) == down) {
+            depth += std::stoul(line.substr(down.size()));
+        }
+        if (line.size() > up.size() && line.substr(0,up.size()) == up) {
+            depth -= std::stoul(line.substr(up.size()));
+        }
+    }
+
+    std::cout << "Distance * depth: " << horiz << " * " << depth << " = " << horiz * depth << '\n';
+}

2021/puzzle-02-02.cc

@@ -0,0 +1,35 @@
+//
+// Created by Matthew Gretton-Dann on 02/12/2021.
+//
+
+#include <string>
+#include <iostream>
+
+int main()
+{
+    using namespace std::string_literals;
+
+    static const auto fwd{"forward "s};
+    static const auto down{"down "s};
+    static const auto up{"up "s};
+
+    std::string line;
+    unsigned long horiz{0};
+    unsigned long depth{0};
+    unsigned long aim{0};
+    while (std::getline(std::cin, line)) {
+        if (line.size() > fwd.size() && line.substr(0,fwd.size()) == fwd) {
+            auto dist{std::stoul(line.substr(fwd.size()))};
+            horiz += dist;
+            depth += aim * dist;
+        }
+        if (line.size() > down.size() && line.substr(0,down.size()) == down) {
+            aim += std::stoul(line.substr(down.size()));
+        }
+        if (line.size() > up.size() && line.substr(0,up.size()) == up) {
+            aim -= std::stoul(line.substr(up.size()));
+        }
+    }
+
+    std::cout << "Distance * depth: " << horiz << " * " << depth << " = " << horiz * depth << '\n';
+}