Skip to content

Instantly share code, notes, and snippets.

@gingemonster
Last active December 5, 2016 22:00
Show Gist options
  • Save gingemonster/1e9a293ae40d8c6e5aac6d030678c092 to your computer and use it in GitHub Desktop.
Save gingemonster/1e9a293ae40d8c6e5aac6d030678c092 to your computer and use it in GitHub Desktop.
Adventofcode Day 5 - Challenge 2
using System;
using System.Security.Cryptography;
using System.Text;
using System.Linq;
using System.Diagnostics;
namespace ConsoleApplication
{
public class Program
{
public static void Main(string[] args)
{
var input = "abbhdwsy";
var index = 0;
var password = new string[8];
var startTime = Process.GetCurrentProcess().StartTime;
var md5Hash = MD5.Create();
{
while(true){
var hash = GetMd5Hash(md5Hash, input + index);
if(startsWithFiveZeros(hash)){
CalculateNextPasswordCharacter(hash, password);
if(password.Count(p => p!=null) == 8) break;
}
index++;
}
}
Console.WriteLine(String.Join("", password));
Console.WriteLine(DateTime.Now - Process.GetCurrentProcess().StartTime);
}
private static void CalculateNextPasswordCharacter(string hash, string[] password){
var partOfHash = hash.Substring(5,1);
if(!IsDigitsOnly(partOfHash)) return;
var passIndex = Convert.ToInt16(partOfHash);
if (passIndex > 7) return;
if(password[passIndex]==null) password[passIndex] = hash.Substring(6,1);
}
private static bool IsDigitsOnly(string str)
{
foreach (char c in str)
{
if (c < '0' || c > '9')
return false;
}
return true;
}
private static string GetMd5Hash(MD5 md5Hash, string input)
{
// Convert the input string to a byte array and compute the hash.
byte[] data = md5Hash.ComputeHash(Encoding.ASCII.GetBytes(input));
// Return the hexadecimal string.
return StringExtensions.ToHex(data);
}
private static bool startsWithFiveZeros(string input){
return input.Substring(0,5) == "00000";
}
}
public static class StringExtensions{
/// <summary>
/// Hex string lookup table.
/// </summary>
private static readonly string[] HexStringTable = new string[]
{
"00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "0A", "0B", "0C", "0D", "0E", "0F",
"10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "1A", "1B", "1C", "1D", "1E", "1F",
"20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "2A", "2B", "2C", "2D", "2E", "2F",
"30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "3A", "3B", "3C", "3D", "3E", "3F",
"40", "41", "42", "43", "44", "45", "46", "47", "48", "49", "4A", "4B", "4C", "4D", "4E", "4F",
"50", "51", "52", "53", "54", "55", "56", "57", "58", "59", "5A", "5B", "5C", "5D", "5E", "5F",
"60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "6A", "6B", "6C", "6D", "6E", "6F",
"70", "71", "72", "73", "74", "75", "76", "77", "78", "79", "7A", "7B", "7C", "7D", "7E", "7F",
"80", "81", "82", "83", "84", "85", "86", "87", "88", "89", "8A", "8B", "8C", "8D", "8E", "8F",
"90", "91", "92", "93", "94", "95", "96", "97", "98", "99", "9A", "9B", "9C", "9D", "9E", "9F",
"A0", "A1", "A2", "A3", "A4", "A5", "A6", "A7", "A8", "A9", "AA", "AB", "AC", "AD", "AE", "AF",
"B0", "B1", "B2", "B3", "B4", "B5", "B6", "B7", "B8", "B9", "BA", "BB", "BC", "BD", "BE", "BF",
"C0", "C1", "C2", "C3", "C4", "C5", "C6", "C7", "C8", "C9", "CA", "CB", "CC", "CD", "CE", "CF",
"D0", "D1", "D2", "D3", "D4", "D5", "D6", "D7", "D8", "D9", "DA", "DB", "DC", "DD", "DE", "DF",
"E0", "E1", "E2", "E3", "E4", "E5", "E6", "E7", "E8", "E9", "EA", "EB", "EC", "ED", "EE", "EF",
"F0", "F1", "F2", "F3", "F4", "F5", "F6", "F7", "F8", "F9", "FA", "FB", "FC", "FD", "FE", "FF"
};
/// <summary>
/// Returns a hex string representation of an array of bytes.
/// </summary>
/// <param name="value">The array of bytes.</param>
/// <returns>A hex string representation of the array of bytes.</returns>
public static string ToHex(this byte[] value)
{
var stringBuilder = new StringBuilder();
if (value != null)
{
foreach (var b in value)
{
stringBuilder.Append(HexStringTable[b]);
}
}
return stringBuilder.ToString();
}
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment