Add day 1 of 2021's puzzles.

2021/puzzle-01-01.cc

@@ -0,0 +1,23 @@
+//
+// Created by Matthew Gretton-Dann on 01/12/2021.
+//
+
+#include <cstdlib>
+#include <limits>
+#include <string>
+#include <iostream>
+
+int main(void) {
+    unsigned long prev{std::numeric_limits<unsigned long>::max()};
+    unsigned incrs{0};
+    std::string line;
+    while (std::getline(std::cin, line)) {
+        auto current{std::stoul(line)};
+        if (current > prev) {
+            ++incrs;
+        }
+        prev = current;
+    }
+    std::cout << "Number of increments: " << incrs << '\n';
+    return EXIT_SUCCESS;
+}