高精度运算c++模板（加减乘、高精度除低精度及取模）

包括高精度间的加、减、乘，及高精度除低精度，正数高精度模低精度

#include <iostream>
#include <string>
#include <algorithm>
#include <iomanip>
using namespace std;

struct BigInt {
	int num[1000];
	int len;
	bool symbol;
	BigInt() {
		fill(num, num + 1000, 0);
		len = 0;
		symbol = true;
	}
	void set(string str) {
		int tmp = 0;
		int weight = 1;
		if (str[0] == '-') {
			symbol = false;
			str = str.substr(1);
		}
		for (int i = str.size() - 1; i >= 0; i--) {
			tmp += (str[i] - '0') * weight;
			weight *= 10;
			if (weight == 10000 || i == 0) {
				num[len] = tmp;
				tmp = 0;
				weight = 1;
				len++;
			}
		}
	}
	void output() {
		if (!symbol && !(len == 1 && num[0] == 0))
			cout << '-';
		cout << num[len - 1];
		for (int i = len - 2; i >= 0; i--) {
			cout << setw(4) << setfill('0') << num[i];
		}
		cout << endl;
	}
	BigInt operator + (BigInt b) {
		BigInt res;
		//处理符号
		if (!symbol &&a