大数相乘

悠悠 2022-08-20 06:29 176阅读 0赞

参考地址：[http://www.cnblogs.com/heyonggang/p/3599857.html][http_www.cnblogs.com_heyonggang_p_3599857.html]

代码如下：

/*****************************************************************************
    Prototype    : multiply
    Description  : 两个任意长度的长整数相乘, 输出结果
    Input Param  :
    const std::string strMultiplierA  乘数A
    const std::string strMultiplierB  乘数B
    Output       :
    std::string strRst            乘法结果
    Return Value :
    int                       0  正确
    -1  异常
    *****************************************************************************/
    int multiply(const std::string strMultiplierA, const std::string strMultiplierB, std::string &strRst)
    {
    
    	if (strMultiplierA.length() == 0 || strMultiplierB.length() == 0)
    	{
    		return -1;
    	}
    	
    		
    	/* 在这里实现功能 */
    	vector<int> vecA, vecB, vecC;
    	string strA = strMultiplierA;
    	int i = 0, j = 0;
    
    	/*将字符串转换为数字并翻转*/
    
    	/*将字符串转换为数字并翻转*/
    	for (i = strA.size() - 1; i >= 0; i--)
    	{
    		vecA.push_back(strA[i] - '0');
    	}
    
    	for (i = strMultiplierB.size() - 1; i >= 0; i--)
    	{
    		vecB.push_back(strMultiplierB[i] - '0');
    	}
    
    	
    	vecC.resize(vecA.size() + vecB.size());
    
    	/**逐位相乘*/
    	
    	for (i = 0; i < vecA.size(); i++)
    	{
    		for (j = 0; j < vecB.size(); j++)
    		{
    			vecC[i + j] += vecA[i] * vecB[j]; 
    		}
    	}
    	
    
    	/*消除进位*/
    	for (i = vecC.size() - 1; i >= 0; i--)
    	{
    		if (vecC[i] != 0)
    		{
    			break;
    		}
    		else
    		{
    			vecC.pop_back();
    		}
    	}
    	int c = 0;
    	for (i = 0; i < vecC.size(); i++)
    	{
    		vecC[i] += c;
    		c = vecC[i] / 10;
    		vecC[i] = vecC[i] % 10;
    	}
    	if (c != 0)
    	{
    		vecC.push_back(c);
    	}
    
    	/*将计算结果转换为字符串并翻转*/
    	for (i = 0; i < vecC.size(); i++)
    	{
    		strRst.push_back(char(vecC[i] + '0'));
    	}
    
    	reverse(strRst.begin(), strRst.end());
    	
    	return 0;
    }

[http_www.cnblogs.com_heyonggang_p_3599857.html]: http://www.cnblogs.com/heyonggang/p/3599857.html