public static string LongestWord(string[] words)
{
Dictionary <string, bool> results = new Dictionary <string, bool>();
foreach (string word in words)
{
results[word] = true;
}
foreach (string word in words.OrderByDescending(s => s.Length))
{
if (LongestWordClass.CanBuild(word, true, results))
{
return(word);
}
}
return(string.Empty);
}
private static bool CanBuild(string s, bool isWord, Dictionary <string, bool> results)
{
bool result = false;
if (!isWord && results.TryGetValue(s, out result))
{
return(result);
}
result = false;
for (int i = 1; i < s.Length - 1; i++)
{
if (LongestWordClass.CanBuild(s.Substring(0, i), false, results) && LongestWordClass.CanBuild(s.Substring(i), false, results))
{
result = true;
break;
}
}
results[s] = result;
return(result);
}