代码是这样的：

#include <bits/stdc++.h>
using namespace std;

int main() {
	string a1, b1;
	int a[1000000000000], b[1000000000000], c[10000000000000], lena, lenb, lenc, i, x;
	memset(a, 0, sizeof(a));
	memset(b, 0, sizeof(b));
	memset(c, 0, sizeof(c));
	getline(cin, a1);
	getline(cin, b1);
	lena = a1.size();
	lenb = b1.size();
	for (i = 0; i <= lena - 1; i++)
		a[lena - i] = a1[i] - 48;
	for (i = 0; i <= lenb - 1; i++)
		b[lenb - i] = b1[i] - 48;
	lenc = 1;
	x = 0;
	while (lenc <= lena || lenc <= lenb) {
		c[lenc] = a[lenc] + b[lenc] + x;
		x = c[lenc] / 10;
		c[lenc] %= 10;
		lenc++;
	}
	c[lenc] = x;
	if (c[lenc] == 0)
		lenc--;
	for (i = lenc; i >= 1; i--)
		cout << c[i];
	return 0;
}