Add 2016 Day 3 puzzles

2016/puzzle-03-01.cc

@@ -0,0 +1,48 @@
+//
+// Created by Matthew Gretton-Dann on 03/12/2021.
+//
+
+#include <array>
+#include <cctype>
+#include <iostream>
+#include <string>
+
+struct Triangle
+{
+  explicit Triangle(std::string const& s)
+  {
+    std::size_t idx{0};
+    for (unsigned i = 0; i < 3; ++i) {
+      while (idx < s.size() && std::isspace(s[idx]) != 0) {
+        ++idx;
+      }
+      assert(idx < s.size());
+      std::size_t end{0};
+      lengths_[i] = std::stoul(s.substr(idx), &end);
+      idx += end;
+    }
+  }
+
+  [[nodiscard]] auto is_valid() const -> bool
+  {
+    return (lengths_[0] + lengths_[1]) > lengths_[2] && (lengths_[0] + lengths_[2]) > lengths_[1] &&
+           (lengths_[1] + lengths_[2]) > lengths_[0];
+  }
+
+private:
+  std::array<std::uint64_t, 3> lengths_;
+};
+
+auto main() -> int
+{
+  unsigned valid{0};
+  std::string line;
+  while (std::getline(std::cin, line)) {
+    Triangle triangle{line};
+    if (triangle.is_valid()) {
+      ++valid;
+    }
+  }
+  std::cout << "Number of valid triangles: " << valid << '\n';
+  return 0;
+}