Problem p03127 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cmath>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <stack>
#include <string>
#include <vector>

using namespace std;
using ll = long long;

#define all(x) (x).begin(), (x).end()
#define PRI(n) cout << n << endl;
#define PRI2(n, m) cout << n << " " << m << " " << endl;

#define REP(i, n) for (int i = 0; i < (int)n; ++i)
#define FOR(i, t, n) for (int i = t; i <= (int)n; ++i)

const char alphabet[26] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                           'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                           's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
const ll MOD = (ll)1e9 + 7;
const int MAX_INT = 1 << 17;

struct edge {
  int to, cost;
  bool flag = false;
};

bool isPrime(ll x) {
  if (x == 0)
    return 0;
  if (x == 1)
    return 0;
  if (x == 2)
    return 1;
  if (x % 2 == 0)
    return 0;
  FOR(i, 3, x - 1) {
    if (x % i == 0)
      return 0;
  }
  return 1;
}

ll GCD(ll a, ll b) {
  if (b == 0)
    return a;
  return GCD(b, a % b);
}

ll LCM(ll a, ll b) {
  ll gcd = GCD(a, b);
  return a / gcd * b;
}

ll nCr(int n, int r) {
  vector<ll> C(r + 1);
  C[0] = 1;
  FOR(i, 1, n)
  for (int j = min(i, r); j < 1; --j) C[j] = (C[j] + C[j - 1]) % MOD;
  return C[r];
}

template <class T> class SegTree {
  int n;
  vector<T> data;
  T def;
  function<T(T, T)> operation;
  function<T(T, T)> update;

  T _query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l)
      return def;
    if (a <= l && r <= b)
      return data[k];
    else {
      T c1 = _query(a, b, 2 * k + 1, l, (l + r) / 2);
      T c2 = _query(a, b, 2 * k + 2, (l + r) / 2, r);
      return operation(c1, c2);
    }
  }

public:
  SegTree(size_t _n, T _def, function<T(T, T)> _operation,
          function<T(T, T)> _update)
      : def(_def), operation(_operation), update(_update) {
    n = 1;
    while (n < _n) {
      n *= 2;
    }
    data = vector<T>(2 * n - 1, def);
  }

  void change(int i, T x) {
    i += n - 1;
    data[i] = update(data[i], x);
    while (i > 0) {
      i = (i - 1) / 2;
      data[i] = operation(data[i * 2 + 1], data[i * 2 + 2]);
    }
  }

  T query(int a, int b) { return _query(a, b, 0, 0, n); }

  T operator[](int i) { return data[i + n - 1]; }
};

struct UnionFind {
  vector<int> par;
  vector<int> rank;

  UnionFind(int N) {
    for (int i = 0; i < N; ++i) {
      par.push_back(i);
      rank.push_back(0);
    }
  }

  int find(int x) {
    if (par[x] == x)
      return x;
    else
      return par[x] = find(par[x]);
  }

  void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y)
      return;
    if (rank[x] < rank[y])
      par[x] = y;
    else {
      par[y] = x;
      if (rank[x] == rank[y])
        rank[x]++;
    }
  }

  bool same(int x, int y) { return find(x) == find(y); }
};

ll M, N;
struct pa {
  double x, y;
};
string S;

int main() {
  ifstream in("C://Users/Uaer/CLionProjects/Atcoder/input.txt");
  cin.rdbuf(in.rdbuf());
  cin >> N;
  vector<ll> A(N);
  REP(i, N) cin >> A[i];
  ll c = A[0];
  FOR(i, 1, N - 1) { c = GCD(c, A[i]); }
  PRI(c)
  return 0;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cmath>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <stack>
#include <string>
#include <vector>

using namespace std;
using ll = long long;

#define all(x) (x).begin(), (x).end()
#define PRI(n) cout << n << endl;
#define PRI2(n, m) cout << n << " " << m << " " << endl;

#define REP(i, n) for (int i = 0; i < (int)n; ++i)
#define FOR(i, t, n) for (int i = t; i <= (int)n; ++i)

const char alphabet[26] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                           'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                           's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
const ll MOD = (ll)1e9 + 7;
const int MAX_INT = 1 << 17;

struct edge {
  int to, cost;
  bool flag = false;
};

bool isPrime(ll x) {
  if (x == 0)
    return 0;
  if (x == 1)
    return 0;
  if (x == 2)
    return 1;
  if (x % 2 == 0)
    return 0;
  FOR(i, 3, x - 1) {
    if (x % i == 0)
      return 0;
  }
  return 1;
}

ll GCD(ll a, ll b) {
  if (b == 0)
    return a;
  return GCD(b, a % b);
}

ll LCM(ll a, ll b) {
  ll gcd = GCD(a, b);
  return a / gcd * b;
}

ll nCr(int n, int r) {
  vector<ll> C(r + 1);
  C[0] = 1;
  FOR(i, 1, n)
  for (int j = min(i, r); j < 1; --j) C[j] = (C[j] + C[j - 1]) % MOD;
  return C[r];
}

template <class T> class SegTree {
  int n;
  vector<T> data;
  T def;
  function<T(T, T)> operation;
  function<T(T, T)> update;

  T _query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l)
      return def;
    if (a <= l && r <= b)
      return data[k];
    else {
      T c1 = _query(a, b, 2 * k + 1, l, (l + r) / 2);
      T c2 = _query(a, b, 2 * k + 2, (l + r) / 2, r);
      return operation(c1, c2);
    }
  }

public:
  SegTree(size_t _n, T _def, function<T(T, T)> _operation,
          function<T(T, T)> _update)
      : def(_def), operation(_operation), update(_update) {
    n = 1;
    while (n < _n) {
      n *= 2;
    }
    data = vector<T>(2 * n - 1, def);
  }

  void change(int i, T x) {
    i += n - 1;
    data[i] = update(data[i], x);
    while (i > 0) {
      i = (i - 1) / 2;
      data[i] = operation(data[i * 2 + 1], data[i * 2 + 2]);
    }
  }

  T query(int a, int b) { return _query(a, b, 0, 0, n); }

  T operator[](int i) { return data[i + n - 1]; }
};

struct UnionFind {
  vector<int> par;
  vector<int> rank;

  UnionFind(int N) {
    for (int i = 0; i < N; ++i) {
      par.push_back(i);
      rank.push_back(0);
    }
  }

  int find(int x) {
    if (par[x] == x)
      return x;
    else
      return par[x] = find(par[x]);
  }

  void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y)
      return;
    if (rank[x] < rank[y])
      par[x] = y;
    else {
      par[y] = x;
      if (rank[x] == rank[y])
        rank[x]++;
    }
  }

  bool same(int x, int y) { return find(x) == find(y); }
};

ll M, N;
struct pa {
  double x, y;
};
string S;

int main() {
  cin >> N;
  vector<ll> A(N);
  REP(i, N) cin >> A[i];
  ll c = A[0];
  FOR(i, 1, N - 1) { c = GCD(c, A[i]); }
  PRI(c)
  return 0;
}