aoc 2016, days 4, 5, 6

1 files changed, 74 insertions, 0 deletions

diff --git a/2016/src/day05.cpp b/2016/src/day05.cpp
new file mode 100644
index 0000000..dfce653
--- /dev/null
+++ b/2016/src/day05.cpp
@@ -0,0 +1,74 @@
+// Standard C++
+#include <array>
+#include <fstream>
+#include <iostream>
+#include <string>
+
+// Standard C
+#include <cstdlib> // memcmp
+
+// System
+#include <md5.h>
+
+using namespace std;
+
+void
+part1(string_view puzzle)
+{
+        array<char, MD5_DIGEST_STRING_LENGTH> digest{};
+
+        string result;
+
+        string input;
+        for ( unsigned long counter = 0;; ++counter ) {
+                input = puzzle;
+                input += to_string(counter);
+                MD5Data(input.data(), input.size(), digest.data());
+
+                if ( memcmp(digest.data(), "00000", 5) == 0 ) {
+                        result += digest.at(5);
+                        if ( result.length() == 8 ) {
+                                cout << result << endl;
+                                return;
+                        }
+                }
+        }
+}
+
+void
+part2(string_view puzzle)
+{
+        array<char, MD5_DIGEST_STRING_LENGTH> digest{};
+
+        string result = "________";
+
+        string input;
+        for ( unsigned long counter = 0;; ++counter ) {
+                input = puzzle;
+                input += to_string(counter);
+                MD5Data(input.data(), input.size(), digest.data());
+
+                if ( memcmp(digest.data(), "00000", 5) == 0 ) {
+                        auto position = digest.at(5) - '0';
+                        if ( position < 0 || position > 7 ) {
+                                continue;
+                        }
+                        if ( result.at(size_t(position)) != '_' ) {
+                                continue;
+                        }
+                        result.at(size_t(position)) = digest.at(6);
+                        if ( result.find('_') == string::npos ) {
+                                cout << result << endl;
+                                return;
+                        }
+                }
+        }
+}
+
+int
+main()
+{
+        auto puzzle = "reyedfim"s;
+        part1(puzzle);
+        part2(puzzle);
+}