Problem of the Day
A new programming or logic puzzle every Mon-Fri

Comments:

• Anonymous - 9 years, 11 months ago

  C# quick and dirty console app

  1 - http request to get the html for the Past Problems page

  2 - parse out the list items containing the problem names

  3 - check these names against a list of previous problems, if a new problem is found output it to the console and add it to the list.

  4 - Sleep for 5 min and repeat.

  Next step would be to store the previous problems in a file and also grab date added information.

  Code :

  public class Program
  {
      public const string PAST_PROBLEMS_URL = "http://www.problemotd.com/past/";
  
      static void Main(string[] args)
      {
          var pastProblems = new List<string>();
  
          while (true)
          {
              var problems = GetProblemList();
  
              foreach (var problem in problems)
              {
                  if (!pastProblems.Contains(problem))
                  {
                      Console.WriteLine("New Problem : {0}", problem);
                      pastProblems.Add(problem);
                  }
              }
  
              Thread.Sleep(300000);
          }
      }
  
      private static List<string> GetProblemList()
      {
          string pastProblemsHtml = "";
          var webRequest = HttpWebRequest.Create(PAST_PROBLEMS_URL);
          webRequest.Method = "GET";
  
          var webResponse = (HttpWebResponse)webRequest.GetResponse();
          using (var responseStream = new StreamReader(webResponse.GetResponseStream()))
          {
              pastProblemsHtml = responseStream.ReadToEnd();
              responseStream.Close();
          }
  
          return ParsePastProblemsHtml(pastProblemsHtml);
      }
  
      private static List<string> ParsePastProblemsHtml(string ppHtml)
      {
          var listItemList = new List<string>();
  
          for(int i = 0; i < ppHtml.Length - 4; i++)
          {
              if (ppHtml.Substring(i, 4).Equals("<li>"))
              {
                  bool isMatch = false;
                  for (int j = 1; j < ppHtml.Length - i && !isMatch; j++)
                  {
                      if (Regex.IsMatch(ppHtml.Substring(i, j), @"^<li>.*</li>$"))
                      {
                          isMatch = true;
                          listItemList.Add(ppHtml.Substring(i, j));
                          i = i + j;
                      }
                  }
              }
          }
  
          listItemList = listItemList.Where(s => !s.Contains("a href=\"/suggest")).ToList();
  
          var problemList = new List<string>();
          foreach (var problemListItem in listItemList)
          {
              for (int i = 0; i < problemListItem.Length - 2; i++)
              {
                  if (problemListItem.Substring(i, 2).Equals("\">"))
                  {
                      bool isMatch = false;
                      for (int j = 1; j < problemListItem.Length - i && !isMatch; j++)
                      {
                          if (Regex.IsMatch(problemListItem.Substring(i + 1, j), @"^>.*</a>$"))
                          {
                              isMatch = true;
                              problemList.Add(problemListItem.Substring(i + 2, j-5));
                              i = i + j;
                          }
                      }
                  }
              }
          }
  
          return problemList;
      }
  }
  

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