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#include "stdafx.h"<br /> #include <string.h><br /> // 字符串反转<br /> void reverse_string(char* pszBuffer)<br /> {<br /> unsigned int length = strlen(pszBuffer);<br /> for (size_t i = 0; i < length / 2; i++)<br /> {<br /> char temp = pszBuffer[i];<br /> pszBuffer[i] = pszBuffer[length - i - 1];<br /> pszBuffer[length - i - 1] = temp;<br /> }<br /> }<br /> // 个位数与大整数的乘法<br /> void multiply_one_digits(const char* numToMultiple, char* pResultBuffer, unsigned char num)<br /> {<br /> unsigned int length = strlen(numToMultiple);<br /> unsigned int adjust = 0;<br /> unsigned int index = 0;<br /> unsigned int i = 0;<br /> while (i < length)<br /> {<br /> unsigned char charToMultiply = numToMultiple[i];<br /> unsigned int numToMultiply = charToMultiply - 0x30;<br /> unsigned int result = numToMultiply * num + adjust;<br /> adjust = result / 10;<br /> result = result % 10;<br /> pResultBuffer[index++] = (char)(result + 0x30);<br /> i++;<br /> }<br /> if (adjust != 0)<br /> {<br /> pResultBuffer[index] = (char)(adjust + 0x30);<br /> }<br /> }<br /> //去除小数点前无效的0，如0.1234最后会转化为1234<br /> void remove_zero(char* number)<br /> {<br /> size_t i = 0;<br /> while (number[i] == '0')<br /> {<br /> size_t len = strlen(number);<br /> for (int j = 0; j < len - 1; j++)<br /> {<br /> number[j] = number[j+1];<br /> }<br /> number[j] = '/0';<br /> }<br /> }<br /> // 去除乘数里的小数点<br /> void remove_dot(char* number)<br /> {<br /> remove_zero(number);<br /> size_t remove_index = 0;<br /> bool need_remove = false;<br /> size_t len = strlen(number);<br /> for (size_t i = 0; i < len; i++)<br /> {<br /> if (number[i] == '.')<br /> {<br /> need_remove = (i == 0 ? true : false);<br /> while (i < len - 1)<br /> {<br /> char ch_next = number[i+1];<br /> number[i] = ch_next;<br /> i++;<br /> }<br /> number[len - 1] = '/0';<br /> break;<br /> }<br /> }<br /> if (need_remove)<br /> {<br /> remove_zero(number);<br /> }<br /> }<br /> // 去掉小数点后无效的0<br /> void trim_zero(char* number)<br /> {<br /> unsigned int len = strlen(number);<br /> if (number[0] == '0')<br /> {<br /> for (size_t i = 0; i < len - 1; i++)<br /> {<br /> number[i] = number[i+1];<br /> }<br /> number[i] = '/0';<br /> }<br /> }<br /> // 初始化被乘数<br /> void setup_num(char* result, const char* num_multiplyed, unsigned int pos)<br /> {<br /> strcpy(result, num_multiplyed);<br /> while (pos > 0)<br /> {<br /> unsigned int len = strlen(result);<br /> for (size_t i = len; i > 0; i--)<br /> {<br /> result[i] = result[i-1];<br /> }<br /> result[0] = '0';<br /> result[len + 1] = '/0';<br /> pos--;<br /> }<br /> }<br /> // 保存一次计算的结果<br /> void save_result(char* pResultBuffer, char* added)<br /> {<br /> unsigned int adjust = 0;<br /> if (strlen(pResultBuffer) < strlen(added))<br /> {<br /> unsigned append_len = strlen(added) - strlen(pResultBuffer);<br /> for (size_t j = 0; j < append_len; j++)<br /> {<br /> strcat(pResultBuffer, "0");<br /> }<br /> }<br /> for (size_t i = 0; i < strlen(pResultBuffer); i++)<br /> {<br /> unsigned int current = pResultBuffer[i] - 0x30;<br /> char to_add = '0';<br /> if (i < strlen(added))<br /> {<br /> to_add = added[i];<br /> }<br /> else<br /> {<br /> int test = 0;<br /> }<br /> unsigned int value = current + adjust + to_add - 0x30;<br /> adjust = value / 10;<br /> pResultBuffer[i] = value % 10 + 0x30;<br /> }<br /> if (adjust != 0)<br /> {<br /> pResultBuffer[i] = adjust + 0x30;<br /> pResultBuffer[i+1] = '/0';<br /> }<br /> }<br /> // 如果乘1000，则移动3位，该函数通过补0达到移位的目的<br /> void insert_zero(char* pResultBuffer, unsigned int zero_num)<br /> {<br /> size_t i = zero_num;<br /> while (i)<br /> {<br /> size_t len = strlen(pResultBuffer);<br /> for (size_t j = len; j > 0; j--)<br /> {<br /> pResultBuffer[j] = pResultBuffer[j-1];<br /> }<br /> pResultBuffer[0] = '0';<br /> i--;<br /> }<br /> }<br /> // 调整计算结果：在正确的位置插入小数点<br /> void adjust_result(char* pResultBuffer, unsigned int move_right_bits)<br /> {<br /> unsigned int len = strlen(pResultBuffer);<br /> if (move_right_bits > 0)<br /> {<br /> if (move_right_bits > len)<br /> {<br /> insert_zero(pResultBuffer, move_right_bits - len);<br /> len = strlen(pResultBuffer);<br /> }<br /> for (size_t i = len; i > len - move_right_bits ; i--)<br /> {<br /> pResultBuffer[i] = pResultBuffer[i-1];<br /> }<br /> pResultBuffer[len - move_right_bits] = '.';<br /> }<br /> if (pResultBuffer[0] == '.')<br /> {<br /> unsigned result_len = strlen(pResultBuffer);<br /> for (size_t j = result_len; j > 0; j--)<br /> {<br /> pResultBuffer[j] = pResultBuffer[j-1];<br /> }<br /> pResultBuffer[0] = '0';<br /> }<br /> }<br /> // 大数相乘的函数<br /> void multiply_huge( char* num_be_multiplyed, char* multiplyer, char* pResultBuffer)<br /> {<br /> unsigned int dot_pos_num1 = 0;<br /> unsigned int dot_pos_num2 = 0;<br /> char ch = '.';<br /> char* pdest1 = strchr(num_be_multiplyed, ch);<br /> char* pdest2 = strchr(multiplyer, ch);<br /> unsigned int move_right_1 = 0;<br /> if (pdest1 != NULL)<br /> {<br /> move_right_1 = (strlen(num_be_multiplyed) - (pdest1 - num_be_multiplyed) - 1);<br /> }<br /> unsigned int move_right_2 = 0;<br /> if (pdest2 != NULL)<br /> {<br /> move_right_2 = (strlen(multiplyer) - (pdest2 - multiplyer) - 1);<br /> }<br /> remove_dot(num_be_multiplyed);<br /> remove_dot(multiplyer);</p> <p> trim_zero(num_be_multiplyed);<br /> trim_zero(multiplyer);<br /> reverse_string(num_be_multiplyed);<br /> reverse_string(multiplyer);<br /> char* num_multiplyed = num_be_multiplyed;<br /> for (size_t i = 0; i < strlen(multiplyer); i++)<br /> {<br /> char* num_to_multiplied = new char[strlen(num_be_multiplyed) + i + 1];<br /> memset(num_to_multiplied, 0, strlen(num_be_multiplyed) + i + 1);<br /> char* pTempResult = new char[strlen(num_be_multiplyed) + i + 2];<br /> memset(pTempResult, 0, strlen(num_be_multiplyed) + i + 2);<br /> setup_num(num_to_multiplied, num_multiplyed, i);<br /> multiply_one_digits(num_to_multiplied, pTempResult, multiplyer[i] - 0x30);<br /> save_result(pResultBuffer, pTempResult);<br /> delete [] pTempResult;<br /> delete [] num_to_multiplied;<br /> }<br /> reverse_string(num_be_multiplyed);<br /> reverse_string(multiplyer);<br /> reverse_string(pResultBuffer);<br /> unsigned int move_right = move_right_1 + move_right_2;<br /> adjust_result(pResultBuffer, move_right);<br /> }<br /> // Test Sample<br /> int main()<br /> {<br /> char* pBuffer = new char[100];<br /> memset(pBuffer, 0, 100);<br /> char multiplied[] = "111111111110.2";<br /> char multiplyer[] = "22222222222.3";<br /> multiply_huge(multiplied, multiplyer, pBuffer);</p> <p> printf("%s/r/n", pBuffer);<br /> delete [] pBuffer;<br /> pBuffer = NULL;<br /> return 0;<br /> }
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