大数相乘算法

#include <stdio.h>#include <string.h>#define MAX_LENGTH 1000/************************************************************************//* 功能：计算两个超大数的乘积/* 参数：source1：被乘数，字符型数组，长度最大为MAX_LENGTH/*       source2：乘数，字符型数组，长度最大为MAX_LENGTH/*       result：计算结果，并返回/************************************************************************/void Multiply(char *source1, char *source2, char *result){int i, j, k, m, n, temp;char tempArr[MAX_LENGTH + 1];    int length1, length2;int carryBit = 0;int start = 0;length1 = strlen(source1);length2 = strlen(source2);for (i = 0; i < MAX_LENGTH; i++){result[i] = '0';}for (i = length1 - 1; i >= 0; i--){k = 0;carryBit = 0;for (j = length2 - 1; j >= 0; j--) {temp = (source2[j] - '0') * (source1[i] - '0') + carryBit;tempArr[k++] = temp % 10 + '0';carryBit = temp / 10;}while (carryBit != 0){tempArr[k++] = carryBit % 10 + '0';carryBit /= 10;}        for (m = start, n = 0; n < k; m++, n++)        {temp = result[m] - '0' +  tempArr[n] - '0' + carryBit;carryBit = temp / 10;result[m] = temp % 10 + '0';        }while (carryBit){result[++m] = carryBit % 10 + '0';carryBit /= 10;}start++;}    result[++m] = '\0';}int main(){char source1[MAX_LENGTH];char source2[MAX_LENGTH];char result[MAX_LENGTH];int i, begin;scanf("%s%s", source1, source2);Multiply(source1, source2, result);// 找到最后一个前导0的位置begin = strlen(result) - 1;for (i = begin; i >= 0; i--){if (result[i] == '0'){begin--;}else{break;}}for (i = begin; i >= 0; i--){printf("%c", result[i]);}putchar(10);return 0;}