Problem p02730 (C++) — buggy submission, verdict: Runtime Error

#include "bits/stdc++.h"

using namespace std;

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef long long LL;
typedef priority_queue<int> PQ_DESC;
typedef priority_queue<int, vector<int>, greater<int>> PQ_ASC;
typedef priority_queue<PII> PQ_DESC_PII;
typedef priority_queue<PII, vector<PII>, greater<PII>> PQ_ASC_PII;

#define ALL(c) (c).begin(), (c).end()
#define PB push_back
#define MP make_pair
#define SORT_ASC(c) sort(ALL(c))
#define SORT_DESC(c) sort(ALL(c), greater<typeof(*((c).begin()))>())
#define SIZE(a) int((a).size())

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define ROF(i, a, b) for (int i = (b - 1); i >= (a); --i)
#define REP(i, n) FOR(i, 0, n)
#define PER(i, n) ROF(i, 0, n)

const double EPS = 1e-10;
const double PI = acos(-1.0);
const int LARGE_INT = 1e9 + 100;
const int INF = 2e9 + 100;
const LL INF_LL = (LL)INF * 300 * 300;
const int MOD = 1e9 + 7;

// debug
#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \\
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \\
       << " " << __FILE__ << endl;

LL modpow(LL a, LL n) {
  LL res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % MOD;
    a = a * a % MOD;
    n >>= 1;
  }
  return res;
}

LL modinv(LL a) {
  LL b = MOD, u = 1, v = 0;
  while (b) {
    LL t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= MOD;
  if (u < 0)
    u += MOD;
  return u;
}

LL moddev(LL a, LL b) { return a * modinv(b) % MOD; }

void Main() {
  string s;
  cin >> s;
  int n = SIZE(s);

  string s_r = s;
  reverse(s_r.begin(), s_r.end());

  if (s_r != s) {
    cout << "No" << endl;
    return;
  }

  string s2;
  FOR(i, 0, (n - 1) / 2) { s2 += s[i]; }
  string s2_r = s2;
  reverse(s2_r.begin(), s2_r.end());

  if (s2_r != s2) {
    cout << "No" << endl;
    return;
  }

  string s3;
  FOR(i, (n + 3) / 2 - 1, n) { s3 += s[i]; }
  string s3_r = s3;
  reverse(s3_r.begin(), s3_r.end());

  if (s3_r != s3) {
    cout << "No" << endl;
    return;
  }

  cout << "Yes" << endl;

  return;
}

int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  Main();
  return 0;
}

Error: 0

Fixed submission:

#include "bits/stdc++.h"

using namespace std;

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef long long LL;
typedef priority_queue<int> PQ_DESC;
typedef priority_queue<int, vector<int>, greater<int>> PQ_ASC;
typedef priority_queue<PII> PQ_DESC_PII;
typedef priority_queue<PII, vector<PII>, greater<PII>> PQ_ASC_PII;

#define ALL(c) (c).begin(), (c).end()
#define PB push_back
#define MP make_pair
#define SORT_ASC(c) sort(ALL(c))
#define SORT_DESC(c) sort(ALL(c), greater<typeof(*((c).begin()))>())
#define SIZE(a) int((a).size())

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define ROF(i, a, b) for (int i = (b - 1); i >= (a); --i)
#define REP(i, n) FOR(i, 0, n)
#define PER(i, n) ROF(i, 0, n)

const double EPS = 1e-10;
const double PI = acos(-1.0);
const int LARGE_INT = 1e9 + 100;
const int INF = 2e9 + 100;
const LL INF_LL = (LL)INF * 300 * 300;
const int MOD = 1e9 + 7;

// debug
#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \\
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \\
       << " " << __FILE__ << endl;

LL modpow(LL a, LL n) {
  LL res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % MOD;
    a = a * a % MOD;
    n >>= 1;
  }
  return res;
}

LL modinv(LL a) {
  LL b = MOD, u = 1, v = 0;
  while (b) {
    LL t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= MOD;
  if (u < 0)
    u += MOD;
  return u;
}

LL moddev(LL a, LL b) { return a * modinv(b) % MOD; }

void Main() {
  string s;
  cin >> s;
  int n = SIZE(s);

  string s_r = s;
  reverse(s_r.begin(), s_r.end());

  string s2 = s.substr(0, (n - 1) / 2);
  string s2_r = s2;
  reverse(s2_r.begin(), s2_r.end());

  string s3 = s.substr((n + 3) / 2 + 1, n - (n + 3) / 2 + 1);
  string s3_r = s3;
  reverse(s3_r.begin(), s3_r.end());

  if (s == s_r && s2 == s2_r && s3 == s3_r) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }

  return;
}

int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  Main();
  return 0;
}