高精度加法

https://www.luogu.org/problemnew/show/P1601

#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
char a1[100],b1[100];
int a[100],b[100],c[100];
int lenc = 0;
void primer(char *a1,char *b1)
{
    //把a1，b1转成字符串倒序存入a,b,下标从1到N
    memset(a,0,sizeof(a)/sizeof(a[0]));
    memset(b,0,sizeof(b)/sizeof(b[0]));

    int lena = strlen(a1);
    int lenb = strlen(b1);
    int r = 0;//进位
    for(int i = 0;i<lena;++i)
    {
        a[lena-i] = a1[i]-'0';//'0'=48
    }
    for(int i = 0;i<lenb;++i)
    {
        b[lenb-i] = b1[i]-'0';//'0'=48
    }
    //模拟加法
     lenc = max(lena,lenb);
    for(int i = 1;i<=lenc;++i)
    {
        c[i] = a[i]+b[i]+r;
        r = c[i]/10;
        c[i] %= 10;
    }
    if(r!=0)
    {
        c[++lenc] = r;
    }
}
int main()
{
    cin >> a1>>b1;
    primer(a1,b1);
    //倒序输出
    for(int i = lenc;i>=1;--i)
    {
        cout << c[i];
    }
    cout << endl;
    return 0;
}