Problem p01228 (C++) — buggy submission, verdict: Runtime Error

// g++ -std=c++11 a.cpp
#include <algorithm>
#include <assert.h>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <typeinfo>
#include <unordered_map>
#include <utility>
#include <vector>
#define loop(i, a, b) for (int i = a; i < b; i++)
#define rep(i, a) loop(i, 0, a)
#define FOR(i, a) for (auto i : a)
#define pb push_back
#define all(in) in.begin(), in.end()
#define shosu(x) fixed << setprecision(x)
using namespace std;
// kaewasuretyuui
typedef long long ll;
// #define int ll
typedef int Def;
typedef pair<Def, Def> pii;
typedef vector<Def> vi;
typedef vector<vi> vvi;
typedef vector<pii> vp;
typedef vector<vp> vvp;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef pair<Def, pii> pip;
typedef vector<pip> vip;
#define mt make_tuple
typedef tuple<int, int, int> tp;
typedef vector<tp> vt;
template <typename A, typename B> bool cmin(A &a, const B &b) {
  return a > b ? (a = b, true) : false;
}
template <typename A, typename B> bool cmax(A &a, const B &b) {
  return a < b ? (a = b, true) : false;
}
// template<class C>constexpr int size(const C &c){return (int)c.size();}
// template<class T,size_t N> constexpr int size(const T
// (&xs)[N])noexcept{return (int)N;}
const double PI = acos(-1);
const double EPS = 1e-9;
Def inf = sizeof(Def) == sizeof(long long) ? 2e18 : 1e9 + 10;
int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};
ll gcd(ll a, ll b) { return (b == 0 ? a : gcd(b, a % b)); }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
int main() {
  int q;
  cin >> q;
  while (q--) {
    int n;
    cin >> n;
    vs in(n);
    rep(i, n) cin >> in[i];

    rep(i, n) {
      int t = in[i].size() / 2;
      rep(j, in[i].size()) if (in[i][j] != '0') t = gcd(t, j / 2);
      if (t == 0) {
        in[i] = "00";
      } else {
        string w = "";
        rep(j, in[i].size() / t / 2) {
          w += in[i][j * 2 * t];
          w += in[i][j * 2 * t + 1];
        }
        in[i] = w;
      }
    }
    ll t = 1;
    rep(i, n) {
      t = lcm(t, in[i].size());
      if (t > 2048)
        break;
    }
    //		rep(i,n)cout<<in[i]<<endl;cout<<endl;
    if (t > 2048)
      cout << "Too complex." << endl;
    else {
      rep(i, n) {
        int w = t / in[i].size();
        string a = "";
        rep(j, in[i].size() / 2) {
          a += in[i][2 * j];
          a += in[i][2 * j + 1];
          a += string(2 * w - 2, '0');
        }
        in[i] = a;
      }
      rep(i, t) {
        int s = 0;
        rep(j, n) s += in[j][i] - '0';
        printf("%01X", s);
      }
      cout << endl;
    }
  }
}


Error: 0

Fixed submission:

// g++ -std=c++11 a.cpp
#include <algorithm>
#include <assert.h>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <typeinfo>
#include <unordered_map>
#include <utility>
#include <vector>
#define loop(i, a, b) for (int i = a; i < b; i++)
#define rep(i, a) loop(i, 0, a)
#define FOR(i, a) for (auto i : a)
#define pb push_back
#define all(in) in.begin(), in.end()
#define shosu(x) fixed << setprecision(x)
using namespace std;
// kaewasuretyuui
typedef long long ll;
// #define int ll
typedef int Def;
typedef pair<Def, Def> pii;
typedef vector<Def> vi;
typedef vector<vi> vvi;
typedef vector<pii> vp;
typedef vector<vp> vvp;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef pair<Def, pii> pip;
typedef vector<pip> vip;
#define mt make_tuple
typedef tuple<int, int, int> tp;
typedef vector<tp> vt;
template <typename A, typename B> bool cmin(A &a, const B &b) {
  return a > b ? (a = b, true) : false;
}
template <typename A, typename B> bool cmax(A &a, const B &b) {
  return a < b ? (a = b, true) : false;
}
// template<class C>constexpr int size(const C &c){return (int)c.size();}
// template<class T,size_t N> constexpr int size(const T
// (&xs)[N])noexcept{return (int)N;}
const double PI = acos(-1);
const double EPS = 1e-9;
Def inf = sizeof(Def) == sizeof(long long) ? 2e18 : 1e9 + 10;
int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};
ll gcd(ll a, ll b) { return (b == 0 ? a : gcd(b, a % b)); }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
int main() {
  int q;
  cin >> q;
  while (q--) {
    int n;
    cin >> n;
    vs in(n);
    rep(i, n) cin >> in[i];

    rep(i, n) {
      int t = in[i].size() / 2;
      rep(j, in[i].size()) if (in[i][j] != '0') t = gcd(t, j / 2);
      if (t == 0) {
        in[i] = "00";
      } else {
        string w = "";
        rep(j, in[i].size() / t / 2) {
          w += in[i][j * 2 * t];
          w += in[i][j * 2 * t + 1];
        }
        in[i] = w;
      }
    }
    ll t = 1;
    rep(i, n) t = lcm(t, in[i].size());
    //		rep(i,n)cout<<in[i]<<endl;cout<<endl;
    if (t > 2048)
      cout << "Too complex." << endl;
    else {
      rep(i, n) {
        int w = t / in[i].size();
        string a = "";
        rep(j, in[i].size() / 2) {
          a += in[i][2 * j];
          a += in[i][2 * j + 1];
          a += string(2 * w - 2, '0');
        }
        in[i] = a;
      }
      rep(i, t) {
        int s = 0;
        rep(j, n) s += in[j][i] - '0';
        printf("%01X", s);
      }
      cout << endl;
    }
  }
}