From 06a24f45a2cb811aaf6b522187d25042ca685d45 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Mon, 11 Nov 2024 20:56:54 +0100
Subject: aoc 2015, day04

---
 2015/src/day04.cpp | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 makefile           |  5 ++++-
 2 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 2015/src/day04.cpp

diff --git a/2015/src/day04.cpp b/2015/src/day04.cpp
new file mode 100644
index 0000000..bc24177
--- /dev/null
+++ b/2015/src/day04.cpp
@@ -0,0 +1,52 @@
+// Standard C++
+#include <array>
+#include <fstream>
+#include <iostream>
+#include <string>
+
+// Standard C
+#include <cstring>
+
+// System
+#include <md5.h>
+
+using namespace std;
+
+void
+brute_force(string_view puzzle, size_t length)
+{
+	array<char, MD5_DIGEST_STRING_LENGTH> digest{};
+
+	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(), "00000000000", length) == 0 ) {
+			cout << digest.data() << ": " << counter << endl;
+			return;
+		}
+	}
+}
+
+void
+part1(string_view puzzle)
+{
+	brute_force(puzzle, 5);
+}
+
+void
+part2(string_view puzzle)
+{
+	brute_force(puzzle, 6);
+}
+
+int
+main()
+{
+	string puzzle = "yzbqklnj";
+
+	part1(puzzle);
+	part2(puzzle);
+}
diff --git a/makefile b/makefile
index d88478f..0c313e7 100644
--- a/makefile
+++ b/makefile
@@ -12,6 +12,9 @@ all: $(patsubst 2015/src/%.cpp,2015/bin/%,$(wildcard 2015/src/*.cpp)) \
 2015/bin/%: 2015/src/%.cpp | 2015/bin
 	c++ $(CPPFLAGS) $^ -o $@
 
+2015/bin/day04: 2015/src/day04.cpp | 2015/bin
+	c++ $(CPPFLAGS) $^ -lmd -o $@
+
 # 2020
 2020/bin/%: 2020/src/%.cpp | 2020/bin
 	c++ $(CPPFLAGS) $^ -o $@
@@ -28,6 +31,6 @@ all: $(patsubst 2015/src/%.cpp,2015/bin/%,$(wildcard 2015/src/*.cpp)) \
 	c++ $(CPPFLAGS) -Wno-sign-conversion -I/usr/local/include $^ -L/usr/local/lib -lz3 -o $@
 
 clean:
-	rm -rf 2020/bin 2022/bin 2023/bin
+	rm -rf 2015/bin 2020/bin 2022/bin 2023/bin
 
 .PHONY: all clean
-- 
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