Problem p03133 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
ll const mod = 998244353;

#define p_ary(ary, a, b, i)                                                    \
  do {                                                                         \
    cout << "[";                                                               \
    for (int(i) = (a); (i) < (b); ++(i))                                       \
      cout << ary[(i)] << ((b)-1 == (i) ? "" : ", ");                          \
    cout << "]\n";                                                             \
  } while (0)
#define p_map(map, it)                                                         \
  do {                                                                         \
    cout << "{";                                                               \
    for (auto(it) = map.begin();; ++(it)) {                                    \
      if ((it) == map.end()) {                                                 \
        cout << "}\n";                                                         \
        break;                                                                 \
      } else                                                                   \
        cout << "" << (it)->first << "=>" << (it)->second << ", ";             \
    }                                                                          \
  } while (0)

ll power_mod(ll a, ll b, ll mod) {
  if (b == 1)
    return a;
  ll c = power_mod(a, b / 2, mod);
  if (b % 2)
    return c * c % mod * a % mod;
  else
    return c * c % mod;
}

int main() {
  int n, m;
  cin >> n >> m;
  bool a[n][m];
  int r = 0;
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j)
      cin >> a[i][j];
  for (int i = 0; i < min(n, m); ++i) {
    int p = i, q = i;
    for (int j = i; j < n; ++j) {
      if (a[p][q])
        break;
      for (int k = i; k < m; ++k)
        if (a[j][k]) {
          p = j;
          q = k;
          break;
        }
    }
    if (!a[p][q])
      break;
    r = i + 1;
    for (int j = i; j < n; ++j)
      swap(a[j][i], a[j][q]);
    for (int j = i; j < m; ++j)
      swap(a[i][j], a[p][j]);
    for (int j = i + 1; j < n; ++j)
      if (a[j][i])
        for (int k = i; k < m; ++k)
          a[j][k] ^= a[i][k];
    for (int j = i + 1; j < m; ++j)
      if (a[i][j])
        for (int k = i; k < n; ++k)
          a[k][j] ^= a[k][i];
  }
  cout << (power_mod(2, n + m - 1, mod) - power_mod(2, n + m - r - 1, mod) +
           mod) %
              mod
       << endl;
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
ll const mod = 998244353;

#define p_ary(ary, a, b, i)                                                    \
  do {                                                                         \
    cout << "[";                                                               \
    for (int(i) = (a); (i) < (b); ++(i))                                       \
      cout << ary[(i)] << ((b)-1 == (i) ? "" : ", ");                          \
    cout << "]\n";                                                             \
  } while (0)
#define p_map(map, it)                                                         \
  do {                                                                         \
    cout << "{";                                                               \
    for (auto(it) = map.begin();; ++(it)) {                                    \
      if ((it) == map.end()) {                                                 \
        cout << "}\n";                                                         \
        break;                                                                 \
      } else                                                                   \
        cout << "" << (it)->first << "=>" << (it)->second << ", ";             \
    }                                                                          \
  } while (0)

ll power_mod(ll a, ll b, ll mod) {
  if (b == 0)
    return 1;
  if (b == 1)
    return a;
  ll c = power_mod(a, b / 2, mod);
  if (b % 2)
    return c * c % mod * a % mod;
  else
    return c * c % mod;
}

int main() {
  int n, m;
  cin >> n >> m;
  bool a[n][m];
  int r = 0;
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j)
      cin >> a[i][j];
  for (int i = 0; i < min(n, m); ++i) {
    int p = i, q = i;
    for (int j = i; j < n; ++j) {
      if (a[p][q])
        break;
      for (int k = i; k < m; ++k)
        if (a[j][k]) {
          p = j;
          q = k;
          break;
        }
    }
    if (!a[p][q])
      break;
    r = i + 1;
    for (int j = i; j < n; ++j)
      swap(a[j][i], a[j][q]);
    for (int j = i; j < m; ++j)
      swap(a[i][j], a[p][j]);
    for (int j = i + 1; j < n; ++j)
      if (a[j][i])
        for (int k = i; k < m; ++k)
          a[j][k] ^= a[i][k];
    for (int j = i + 1; j < m; ++j)
      if (a[i][j])
        for (int k = i; k < n; ++k)
          a[k][j] ^= a[k][i];
  }
  cout << (power_mod(2, n + m - 1, mod) - power_mod(2, n + m - r - 1, mod) +
           mod) %
              mod
       << endl;
  return 0;
}