Problem Statement
象形æåH[0],H[1],â¦,N[n-1]ç»æçé¿åº¦ä¸ºnçåºå称为ä¸ä¸ªå¥åã妿å¥åä¸ä¸åå¨ä¸¤ä¸ªä¸æ iåjï¼0 <= i < j < n - 1ï¼ï¼ä½¿å¾å¥åä¸ç第i个å
ç´ H[i]å第j个å
ç´ H[j]æ¯åä¸ä¸ªè±¡å½¢æåï¼ä¸H[i+1]åH[j+1]æ¯ä¸åç象形æåï¼é£ä¹è¿æ ·çä¸å¥è¯ç§°ä¸ºæ¯âä¸¥æ ¼çâã
å设æk个象形æåï¼è¯·è®¡ç®é¿åº¦ä¸ºnçåºå䏿å¤å°ä¸ªæ¯âä¸¥æ ¼çâã
å设æk个象形æåï¼è¯·è®¡ç®é¿åº¦ä¸ºnçåºå䏿å¤å°ä¸ªæ¯âä¸¥æ ¼çâã
Definition
- Class:
- TheHieroglyphs
- Method:
- count
- Parameters:
- int, int
- Returns:
- long
- Method signature:
- long count(int n, int k)
- (be sure your method is public)
Constraints
- n åk çåå¼å¨1å°18ä¹é´ï¼å«1å18ã
Examples
7
1
Returns: 1
è¿éåªæ1个象形æåï¼æä»¥åªæ1ç§å¥åï¼ä¸æ¯âä¸¥æ ¼âçã1
7
Returns: 7
4
2
Returns: 6
æä»¬ç¨AåB表示è¿2ç§è±¡å½¢æåï¼é£ä¹è½å¤æé åºçé¿åº¦ä¸º4çå¥å为ï¼AAAAãBBBBãABBBãBAAAãABABãBABAã2
4
Returns: 16