求dalao帮助，高精爆零（甚至有TLE）

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int N=505;
char ch;
int len,a[N],b[N],len1,len2,ans[N];
void add(int a[],int b[]){
	len=max(len1,len2);
	for(int i=1;i<=len;++i)
		ans[i]=a[i]+b[i],ans[i+1]+=ans[i]/10,ans[i]%=10;
	if(ans[len+1]) len+=1;
}
int main(){
	while(ch=getchar()){if(ch=='\n') break;a[++len1]=ch-'0';}
	while(ch=getchar()){if(ch=='\n') break;b[++len2]=ch-'0';}
	for(int i=1;i<=len1/2;++i) swap(a[i],a[len1-i+1]);
	for(int i=1;i<=len2/2;++i) swap(b[i],b[len2-i+1]);
	add(a,b);
	for(int i=len;i>=1;i--) printf("%d",ans[i]);
	return 0;
}