Problem 1453 Bignum Arithmetic from http://acm.fzu.edu.cn/problem.php?pid=1453

本文链接：https://blog.youkuaiyun.com/cstur4/article/details/7965829

本文介绍了一种处理大数乘法的方法，通过自定义数组来存储超过常规整型变量所能表示的大数，并实现了两个大数之间的乘法运算。文章提供了一个具体的C++代码示例，展示了如何读取两个大数、执行乘法操作并打印结果。

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Problem 1453 Bignum Arithmetic

Accept: 399 Submit: 1028
Time Limit: 1000 mSec Memory Limit : 32768 KB

Problem Description

In this problem, you will be concerned with integers with very large numbers of digits. You must write code which will repeatedly accept (until end of file) two lines each containing an unsigned integer, and output the product of the two input unsigned integers. The output must not contain any leading zeros.

You can assume that each integer will contain at most 80 digits. The input ends with an end of file.

Sample Input

03421298123

Sample Output

44391636

#include <iostream>
#include <cstdio>
#include <string.h>
using namespace std;
int a[100];
int b[100];
char s1[100];
char s2[100];
int c[200];
int lena, lenb, i, j, len;
void multi(){
    memset(c, 0, sizeof(c));
    len = lena+lenb;

    for(i=0;i<lena;++i)
        for(j=0;j<lenb;++j){
            c[i+j] += a[i]*b[j];
        }
    for(i=0;i<len;++i){
        c[i+1] += c[i]/10;
        c[i] %= 10;
    }

    len++;
    while(len>0 && !c[len-1])
        len--;

}
int main(){


	//freopen("in.txt", "r", stdin);
    while(cin>>s1>>s2){
        lena = strlen(s1);
        lenb = strlen(s2);
        for(i=lena-1;i>=0;--i)
            a[lena-1-i] = s1[i] - '0';
        for(i=lenb-1;i>=0;--i)
            b[lenb-1-i] = s2[i] - '0';
        multi();
        if(len==0)
            printf("0");
        else
            for(i=len-1;i>=0;i--)
                cout<<c[i];
        printf("\n");
    }

	//fclose(stdin);
	return 0;
}