IsIsogram() solution

[Denis_Tynashev]

bool FBullCowGame::IsIsogram(FString Word) const
{
	bool bIsIsogram = true;					// default return value
	TMap <char, bool> LetterSeen;			// Map for Letters

	for (auto Letter : Word)				//looping for each Letter in a given Word 
	{
		Letter = tolower(Letter);			// to handle the mixed letter case
		if (LetterSeen[Letter] == false)	// if the letter was NOT seen before
		{
			LetterSeen[Letter] = true;		// set the letter as seen
		}
		else								//otherwise
		{
			bIsIsogram = false;				// set return value to false
			break;							// out of the loop
		}
	}
	return bIsIsogram;	// return value
}