主体代码：

#include<bits/stdc++.h>
#include"bnio.h"
const int Max = 502;
using namespace std;
char as[Max],bs[Max];
int ai[Max],bi[Max],c[Max];
int maxNum(int a,int b){
	if(a > b) return a;
	return b;
}
void add(){
	int n = 1;
	for( ;n < maxNum(ai[0],bi[0]);n++){
		c[n] = ai[n] + bi[n];
		if(c[n] >= 10){
			c[n + 1] = c[n] / 10;
			c[n] %= 10;
		}
	}
}
int main(void){
	input(as,bs,ai,bi,c);
	add();
	print(c);
	return 0;
}

bnio.h：

#include<bits/stdc++.h>
int x;
void input(char as[ ],char bs[ ],int ai[ ],int bi[ ],int c[ ]){
	x = 1;
	as[0] = getchar();
	while(as[x] != '\n') as[x] = getchar();
	ai[0] = x;
	for(int i = 1;i <= x;i++) ai[i] = as[x - i] - '0';
	x = 1;
	bs[0] = getchar();
	while(bs[x] != '\n') bs[x] = getchar();
	bi[0] = x;
	for(int i = 1;i <= x;i++) bi[i] = bs[x - i] - '0';
}
void print(int c[ ]){
	for(int i = c[0];i > 0;i--) putchar(c[i] + '0');
}