Files
advent-of-code/2016/puzzle-05-02.cc

56 lines
1.5 KiB
C++

#include <algorithm>
#include <array>
#include <cassert>
#include <iostream>
#include <string>
#include <openssl/evp.h>
using MD5Digest = std::array<unsigned char, EVP_MAX_MD_SIZE>;
auto md5(MD5Digest& digest, std::string const& s) -> unsigned int
{
EVP_MD const* md{EVP_md5()};
unsigned int md_len{0};
EVP_MD_CTX* md_context{EVP_MD_CTX_new()};
assert(md_context != nullptr);
EVP_DigestInit_ex2(md_context, md, nullptr);
EVP_DigestUpdate(md_context, s.data(), s.length());
EVP_DigestFinal_ex(md_context, digest.data(), &md_len);
return md_len;
}
auto main() -> int
{
constexpr std::string_view characters{"0123456789abcdef"};
constexpr unsigned password_length{8};
std::string result{"--------"};
std::string line;
if (!std::getline(std::cin, line)) {
std::cerr << "Unable to read from stdin.\n";
return 1;
}
std::uint64_t i{0};
while (std::any_of(result.begin(), result.end(), [](char c) { return c == '-'; })) {
MD5Digest digest;
auto len = md5(digest, line + std::to_string(i));
assert(len >= 3);
if (digest[0] == 0 && digest[1] == 0 && (digest[2] & 0xf0) == 0) {
auto idx{digest[2] & 0xf};
if (idx < password_length) {
if (result.at(idx) == '-') {
result[idx] = characters[(digest[3] & 0xf0) >> 4];
std::cout << '\n';
}
}
}
std::cout << '\r' << result << ' ' << line << i << std::flush;
++i;
}
std::cout << "\nPassword: " << result << '\n';
return 0;
}