ModAdd

input/code.cpp: In function 'int main()':
input/code.cpp:21:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(ll i=0; i<a.size(); i++) {
                 ~^~~~~~~~~
input/code.cpp:22:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       if(i < a.size()-b.size()) {
          ~~^~~~~~~~~~~~~~~~~~~

#include <iostream>
#include <deque>
#include <algorithm>

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef std::string str;

using namespace std;

int main() {
    str a, b;
    cin >> a >> b;
    if (a.size() < b.size()) {
      str c = b;
      b = a;
      a = c;
    }
    str res = "";
    for(ll i=0; i<a.size(); i++) {
      if(i < a.size()-b.size()) {
        res += a[i];
      }
      else {
        int curDig = a[i] - '0',
          nextDig = b[i-(a.size()-b.size())] - '0';
        res += to_string((curDig+nextDig) % 10);
        if (res == "0") {
          res = "";
        }
      }
    }
    if (res == "") {
      res = "0";
    }
    cout << res << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED