From d396dc3221fcf893c885bd9a370b9a30f25b31dd Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Sun, 12 Jan 2025 17:36:26 +0100
Subject: aoc 2016, days 4, 5, 6

---
 2016/src/day05.cpp | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 2016/src/day05.cpp

(limited to '2016/src/day05.cpp')

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);
+}
-- 
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