题解 | 牛牛的加法

#include <iostream>
using namespace std;

int main() {
    std::string a, b;
    std::cin >> a >> b;

    int n = std::max(a.size(), b.size());
    a = std::string(n - a.size(), '0') + a;
    b = std::string(n - b.size(), '0') + b;

    bool ok = false;
    std::string ans = "";
    for(int i = 0;i < n;i += 1){
        int x = a[i] - '0', y = b[i] - '0';
        int c = (x + y) % 10;
        if(c || ok){
            ok = true;
            ans += char('0' + c);
        }
    }

    if(ans.empty()){
        ans = "0";
    }

    std::cout << ans << "\n";
}
// 64 位输出请用 printf("%lld")