if a character of str2 is also present in str1 , then mark its presence as - 1
if ( present [ ord ( str2 [ i ] ) - ord ( ' a ' ) ] == 1 or present [ ord ( str2 [ i ] ) - ord ( ' a ' ) ] == - 1 ) : NEW_LINE INDENT present [ ord ( str2 [ i ] ) - ord ( ' a ' ) ] = - 1 NEW_LINE DEDENT