public IList <string> JoinAdjacentWords(IList <string> wordList, IList <string> keywordsList)
{
if (wordList.Count == keywordsList.Count)
{
return(null);
}
var modifiedPhrases = new HashSet <string>();
var dealtWith = new HashSet <string>();
string firstWord = null, secondWord = null;
for (int i = 0, j = 1; j < wordList.Count; i++, j++)
{
firstWord = wordList[i]; secondWord = wordList[j];
if (keywordsList.Contains(firstWord) && keywordsList.Contains(secondWord))
{
modifiedPhrases.Add($"{firstWord} {secondWord}");
dealtWith.AddMultipleElements <string>(firstWord, secondWord);
}
else
{
if (keywordsList.Contains(firstWord) && !dealtWith.Contains(firstWord))
{
modifiedPhrases.Add(firstWord);
}
//Last Word condition
if (j == wordList.Count - 1 && keywordsList.Contains(secondWord) && !dealtWith.Contains(secondWord))
{
modifiedPhrases.Add(secondWord);
}
}
}
return(modifiedPhrases.ToList());
}