CareerCup

//End user class
Class FileSearcher
{
  //hashtable (targetfolder and indexer mapping)
  private Dictionary<string, Indexer> indexers;
  
  public string SearchText;
  public string targetFolder;
  
  //returns list of files which contains given SearchText
  public List<string> Search(string searchText, string targetFolder)
  {
     if(!indexers.ContainsKey(targetFolder))
	 {
	   indexer = new Indexer();
	   foreach(file f in targetFolder)
	   {
	     ScanFile(f, indexer);
	   }
	   indexers.Add(targetFolder, indexer);
	 }
	 else
	   indexer = indexers[targetFolder];
	   
	return indexer.Search(searchText);
  }
  
  //this function scans the given file and builds the indexer for all the words
  //contained in the file
  private void ScanFile(string fileName, Indexer indexer)
  {
    foreach(string w in file)
	{
		indexer.AddWord(w);
        }
  }
  
}


class Indexer
{
  //adds the given word to a trie, 
  //trie at the end can point to an index(fileID, wordPos) set
  //if the word already exists, it just updates the index(fileID, wordPos) set
  public void AddWord(string w);
  
  //searches in the trie and returns list of files.
  public List<string> Search(string text);
}

It's file search , so interviewer asked me how will you support wild cards in that , user can search for a*p.txt , we should be able to search efficiently.