輸出n對括號的所有有效(左右括號成對匹配)排列

原題：Implement an algorithm to print all valid (e.g., properly opened and closed) combinations of n-pairs of parentheses.   EXAMPLE: input: 3 (e.g., 3 pairs of parentheses) output: ()()(), ()(()), (())(), ((())) [cpp]  void PrintBracketsPairRecs(char *pBegin, char *pCur, int nCurLeft)   {       if (nCurLeft == 1)           {           *pCur = '(';           *(pCur+1) = ')';           printf("%s\n", pBegin); // exit of recursive function           }       else           {           // 1st way: ()*********           *pCur = '(';           *(pCur+1) = ')';           PrintBracketsPairRecs(pBegin, pCur+2, nCurLeft-1);              // 2nd way: (*********)           *pCur = '(';           *(pCur + (nCurLeft)*2 - 1) = ')';           PrintBracketsPairRecs(pBegin, pCur+1, nCurLeft-1);           }   }      void PrintBracketsPair(int n)   {       char *pBuffer = new char[2 * n + 1];       memset(pBuffer, 0, sizeof(char) * 2 * n + 1);       PrintBracketsPairRecs(pBuffer, pBuffer, n);       delete [] pBuffer;   }