#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cmath>
#define maxn 100
using namespace std;
struct bigint{
	int len,a[maxn];
	bigint(int x=0){
		memset(a,0,sizeof(a));
		for(len=1;x;len++)
			a[len]=x%10,x/=10;
		len--;
	}
	int &operator[](int i){
		return a[i];
	}
	void flatten(int L){
		len=L;
		for(int i=1;i<=len;i++)
			a[i+1]+=a[i]/10,a[i]%=10;
		for(;!a[len];)
			len--;
	}
	void print(){
		for(int i=max(len,1);i>=1;i--)
			printf("%d",a[i]);
	}
};
bigint operator+(bigint a,bigint b){
	bigint c;
	int len=max(a.len,b.len);
	for(int i=1;i<=len;i++)
		c[i]+=a[i]+b[i];
	c.flatten(len+1);
	return c;
}
bigint operator*(bigint a,bigint b){
	bigint c;
	int len=a.len;
	for(int i=1;i<=len;i++)
		c[i]=a[i]*b[i];
	c.flatten(len+11);
	return c;
}
int main(){

	return 0;
}

有人可以告诉我这个程序打包再加定义“+”号“*”号哪里错了么？程序报错：10 23 C:\Users\kaila\Desktop\C++\调试.cpp [Error] 'memset' was not declared in this scope

我是直接把深入浅出的程序抄下来的，但是能理解高精度加、乘是怎么算的