#include<bits/stdc++.h>
#include<string.h>
using namespace std;
string x, y;
int a[100000]={0}, b[100000]={0}, c[1000000] = {0}, la, lb, lc;
int main()
{
	cin >> x >> y;
	la = x.length();
	lb = y.length();
	for (int i = 0; i < la; i++)
	{
		a[la - i] = x[i]-'0';
	}
	for (int i = 0; i < la; i++)
	{
		b[lb - i] = y[i]-'0';
	}
	lc = max(la, lb);
	for (int i = 1; i <= lc; i++)
	{
		c[i] += a[i] + b[i];
		c[i + 1] = c[i] / 10;
		c[i] %= 10;
	}
	if (c[lc + 1] > 0)
		lc++;
	for (int i = lc; i >= 1; i--)
	{
		cout << c[i];
	}
	return 0;
}

跟着b站上学的代码，但是只得了60分，遇到999+1111时就会出错，不知道为啥。