大整数加法 模板

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <string>
#include <queue>
#include <stack>
#include <map>
using namespace std;

string add(string a, string b) {
        string s;
        reverse(a.begin(), a.end());
        reverse(b.begin(), b.end());
        int m, k = 0, i = 0;
        while (a[i] && b[i]) {
                m = a[i] - '0' + b[i] - '0' + k;
                k = m / 10;
                s += (m % 10 + '0');
                i ++;
        }
        if (i == a.size()) {
                while (i != b.size()) {
                        m = k + b[i] - '0';
                        k = m / 10;
                        s += m % 10 + '0';
                        i ++;
                }
                if (k) s += k + '0';
        } else if (i == b.size()) {
                while (i != a.size()) {
                        m = k + a[i] - '0';
                        k = m / 10;
                        s += m % 10 + '0';
                        i ++;
                }
                if (k) s += k + '0';
        }
        reverse(s.begin(), s.end());
        return s;
}
int main()
{
        string a, b;
        cin >> a >> b;
        cout << add(a, b) << endl;
}