大数乘法

#include <iostream>#include <fstream>#include <cmath>#include <string>#include <iomanip>#include <algorithm>#include <stdio.h>//using namespace std;std::ifstream cin("in.txt");std::ofstream cout("out.txt");const int LENGHT = 100;/*****************************************功能是大数乘法**技巧：边乘边计算** tmp = c[i+j]+a[i]*b[j]+nCarry; ** 1 2 3** X 1 2** ---------** 2 4 6** 1 2 3** ---------***************************************/void big_multiply(int* a,int* b){int c[LENGHT] ={0};int nCarry = 0;int tmp = 0;for (int i = 0; i<LENGHT; i++){nCarry = 0;for (int j = 0; j<LENGHT-i; j++){tmp = c[i+j]+a[i]*b[j]+nCarry;c[i+j] = tmp%10;nCarry = tmp/10;}}std::memcpy(a,c,sizeof(c));}int main(int argc, char* argv[]){std::string a,b;while (cin>>a>>b){//cout<<big_point_plus(a,b)<<std::endl;int aInt[LENGHT]={0};int bInt[LENGHT]={0};for (int i = a.length()-1,j=0;i>=0;i--){aInt[j++] = a[i]-'0';}for (int i = b.length()-1,j=0;i>=0;i--){bInt[j++] = b[i]-'0';}big_multiply(aInt,bInt);bool nStartOutPut = false;for (int i = LENGHT-1;i>=0;i--){if (nStartOutPut){cout<<aInt[i];} else if(aInt[i]){cout<<aInt[i];nStartOutPut = true;}}cout<<"/n";}return 0;}

大数乘法