Problem p03051 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <complex>
#include <cstdint>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
typedef long long ll;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define revrep(i, n) for (ll i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
void BinarySay(ll x, ll y = 60) {
  rep(i, y) cout << (x >> (y - 1 - i) & 1);
  cout << endl;
}
const ll INFL = 1LL << 60; // 10^18 = 2^60
ll MOD = 1000000007;
// ll MOD = 998244353;
// vector<mint> dp(N, Mint);
// vector<vector<mint>> dp2(N, vector<mint>(N, Mint));
// vector<vector<vector<mint>>> dp3(N, vector<vector<mint>>(N, vector<mint>(N,
// Mint)));
struct mint {
  ll x;
  mint(ll x = 0) : x(x % MOD) {}
  mint &operator+=(const mint a) {
    (x += a.x) %= MOD;
    return *this;
  }
  mint &operator-=(const mint a) {
    (x += MOD - a.x) %= MOD;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  mint &operator%=(const mint a) {
    (x %= a.x);
    return *this;
  }
  mint &operator++(int) {
    (x += 1) %= MOD;
    return *this;
  }
  mint &operator--(int) {
    (x += MOD - 1) %= MOD;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint operator%(const mint a) const {
    mint res(*this);
    return res %= a;
  }
  mint po(ll t) const {
    if (!t)
      return 1;
    mint a = po(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  mint inverse() const { return po(MOD - 2); }
  mint &operator/=(const mint a) { return (*this) *= a.inverse(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
  bool operator==(const mint a) { return this->x == a.x; }
  bool operator!=(const mint a) { return this->x != a.x; }
  void get() { cout << x << endl; }
  void ge() { cout << x << " "; }
};
const mint Mint = 0;

mint pow_mod(ll x, ll k) {
  mint res = 1;
  mint a = x;
  while (k > 0) {
    if (k % 2) {
      res *= a;
    }
    a *= a;
    k /= 2;
  }
  return res;
}

mint inverse(ll x) { return pow_mod(x, MOD - 2); }

// 二項演算
const int MAXcomb = 200010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAXcomb; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
mint comb(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  mint res = fac[n];
  res *= finv[k] * finv[n - k];
  return res;
}
mint comb_naive(ll N, ll K) { // Kが小さい時
  mint res = 1;
  rep(i, K) res *= (N - i);
  mint k = 1;

  rep(i, K) k *= (i + 1);
  res /= k;
  return res;
}
// 第二種スターリング数
const ll MAXStir2 = 3010;
vector<vector<mint>> Stir2memo(MAXStir2, vector<mint>(MAXStir2, Mint));
vector<mint> Bellmemo(MAXStir2, Mint);
void Stir2init() {
  Stir2memo[0][0] = 1;
  rep(i, MAXStir2 - 1) rep(j, i + 1) Stir2memo[i + 1][j + 1] =
      Stir2memo[i][j] + Stir2memo[i][j + 1] * (j + 1);
  rep(i, MAXStir2) {
    Bellmemo[i] = 0;
    rep(j, i + 1) Bellmemo[i] += Stir2memo[i][j];
  }
}
mint Stir2(ll i, ll j) { // 区別できるi個をjグループに分ける場合の数
  if (i < 0 || j < 0 || i < j)
    return 0;
  return Stir2memo[i][j];
}
mint Bell(ll x) { // 区別できるx個をグループ分けする方法全ての場合の数
  if (x < 0)
    return 0;
  return Bellmemo[x];
}
mint kai_mod(ll K) {
  if (K < 0)
    return 0;
  if (K == 0)
    return 1;
  return kai_mod(K - 1) * K;
}

// 約数の列挙O(√n)
vector<ll> divisor(ll n) {
  vector<ll> res(0);
  for (ll i = 1; i * i <= n; i++) {
    if (n % i == 0) {
      res.push_back(i);
      if (i != n / i)
        res.push_back(n / i);
    }
  }
  sort(res.begin(), res.end());
  return res;
}

void compress(vector<ll> &S) {
  vector<ll> xs;
  rep(i, S.size()) xs.push_back(S[i]);
  sort(xs.begin(), xs.end());
  xs.erase(unique(xs.begin(), xs.end()), xs.end());
  rep(i, S.size()) {
    S[i] = lower_bound(xs.begin(), xs.end(), S[i]) - xs.begin();
  }
}

// Range Sum Query
const ll N_ = (1 << 18);
ll seg[2 * N_ - 1];
void add(ll k, ll x) {
  k += N_ - 1;
  seg[k] += x;
  while (k > 0) {
    k = (k - 1) / 2;
    seg[k] = seg[2 * k + 1] + seg[2 * k + 2];
  }
}

ll get_sum(ll x, ll y, ll k = 0, ll left = 0, ll right = N_) {
  if (right <= x || y <= left)
    return 0;
  if (x <= left && right <= y)
    return seg[k];
  ll mid = (left + right) / 2;
  ll l = get_sum(x, y, 2 * k + 1, left, mid);
  ll r = get_sum(x, y, 2 * k + 2, mid, right);
  return l + r;
}

ll N;
vector<ll> A;
void solve() {
  ll XOR = 0;
  ll cnt = 0;
  rep(i, N) XOR ^= A[i];
  if (XOR == 0) {
    ll x = 0;
    vector<ll> B;
    ll now = 0;
    rep(i, N) {
      now ^= A[i];
      B.pb(now);
      if (now == 0) {
        add(i, 1);
        cnt++;
      }
    }
    compress(B);
    ll X = *max_element(B.begin(), B.end());
    vector<ll> L[X + 1];
    rep(i, N) {
      if (B[i] == 0)
        continue;
      L[B[i]].pb(i);
    }
    rep(i, X + 1) L[i].pb(N_);
    mint ans = 0;
    for (ll i = 1; i <= X; i++) {
      if (L[i].size() == 1)
        continue;
      mint s = 0, t = 1;
      for (ll j = 0; j < L[i].size() - 1; j++) {
        ll x = get_sum(L[i][j], L[i][j + 1]);
        s += t;
        t += s * x;
      }
      ans += s;
    }
    ans += pow_mod(2, cnt - 1);
    ans.get();
  } else {
    ll a = XOR;
    ll b = 0;
    ll now = 0;
    mint s = 0, t = 1;
    rep(i, N - 1) {
      now ^= A[i];
      if (now == a) {
        s += t;
      } else if (now == b) {
        t += s;
      }
    }
    t.get();
  }
}

int main() {
  cin >> N;
  A.resize(N);
  rep(i, N) cin >> A[i];
  solve();
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <complex>
#include <cstdint>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
typedef long long ll;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define revrep(i, n) for (ll i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
void BinarySay(ll x, ll y = 60) {
  rep(i, y) cout << (x >> (y - 1 - i) & 1);
  cout << endl;
}
const ll INFL = 1LL << 60; // 10^18 = 2^60
ll MOD = 1000000007;
// ll MOD = 998244353;
// vector<mint> dp(N, Mint);
// vector<vector<mint>> dp2(N, vector<mint>(N, Mint));
// vector<vector<vector<mint>>> dp3(N, vector<vector<mint>>(N, vector<mint>(N,
// Mint)));
struct mint {
  ll x;
  mint(ll x = 0) : x(x % MOD) {}
  mint &operator+=(const mint a) {
    (x += a.x) %= MOD;
    return *this;
  }
  mint &operator-=(const mint a) {
    (x += MOD - a.x) %= MOD;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  mint &operator%=(const mint a) {
    (x %= a.x);
    return *this;
  }
  mint &operator++(int) {
    (x += 1) %= MOD;
    return *this;
  }
  mint &operator--(int) {
    (x += MOD - 1) %= MOD;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint operator%(const mint a) const {
    mint res(*this);
    return res %= a;
  }
  mint po(ll t) const {
    if (!t)
      return 1;
    mint a = po(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  mint inverse() const { return po(MOD - 2); }
  mint &operator/=(const mint a) { return (*this) *= a.inverse(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
  bool operator==(const mint a) { return this->x == a.x; }
  bool operator!=(const mint a) { return this->x != a.x; }
  void get() { cout << x << endl; }
  void ge() { cout << x << " "; }
};
const mint Mint = 0;

mint pow_mod(ll x, ll k) {
  mint res = 1;
  mint a = x;
  while (k > 0) {
    if (k % 2) {
      res *= a;
    }
    a *= a;
    k /= 2;
  }
  return res;
}

mint inverse(ll x) { return pow_mod(x, MOD - 2); }

// 二項演算
const int MAXcomb = 200010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAXcomb; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
mint comb(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  mint res = fac[n];
  res *= finv[k] * finv[n - k];
  return res;
}
mint comb_naive(ll N, ll K) { // Kが小さい時
  mint res = 1;
  rep(i, K) res *= (N - i);
  mint k = 1;

  rep(i, K) k *= (i + 1);
  res /= k;
  return res;
}
// 第二種スターリング数
const ll MAXStir2 = 3010;
vector<vector<mint>> Stir2memo(MAXStir2, vector<mint>(MAXStir2, Mint));
vector<mint> Bellmemo(MAXStir2, Mint);
void Stir2init() {
  Stir2memo[0][0] = 1;
  rep(i, MAXStir2 - 1) rep(j, i + 1) Stir2memo[i + 1][j + 1] =
      Stir2memo[i][j] + Stir2memo[i][j + 1] * (j + 1);
  rep(i, MAXStir2) {
    Bellmemo[i] = 0;
    rep(j, i + 1) Bellmemo[i] += Stir2memo[i][j];
  }
}
mint Stir2(ll i, ll j) { // 区別できるi個をjグループに分ける場合の数
  if (i < 0 || j < 0 || i < j)
    return 0;
  return Stir2memo[i][j];
}
mint Bell(ll x) { // 区別できるx個をグループ分けする方法全ての場合の数
  if (x < 0)
    return 0;
  return Bellmemo[x];
}
mint kai_mod(ll K) {
  if (K < 0)
    return 0;
  if (K == 0)
    return 1;
  return kai_mod(K - 1) * K;
}

// 約数の列挙O(√n)
vector<ll> divisor(ll n) {
  vector<ll> res(0);
  for (ll i = 1; i * i <= n; i++) {
    if (n % i == 0) {
      res.push_back(i);
      if (i != n / i)
        res.push_back(n / i);
    }
  }
  sort(res.begin(), res.end());
  return res;
}

void compress(vector<ll> &S) {
  vector<ll> xs;
  rep(i, S.size()) xs.push_back(S[i]);
  sort(xs.begin(), xs.end());
  xs.erase(unique(xs.begin(), xs.end()), xs.end());
  rep(i, S.size()) {
    S[i] = lower_bound(xs.begin(), xs.end(), S[i]) - xs.begin();
  }
}

// Range Sum Query
const ll N_ = (1 << 20);
ll seg[2 * N_ - 1];
void add(ll k, ll x) {
  k += N_ - 1;
  seg[k] += x;
  while (k > 0) {
    k = (k - 1) / 2;
    seg[k] = seg[2 * k + 1] + seg[2 * k + 2];
  }
}

ll get_sum(ll x, ll y, ll k = 0, ll left = 0, ll right = N_) {
  if (right <= x || y <= left)
    return 0;
  if (x <= left && right <= y)
    return seg[k];
  ll mid = (left + right) / 2;
  ll l = get_sum(x, y, 2 * k + 1, left, mid);
  ll r = get_sum(x, y, 2 * k + 2, mid, right);
  return l + r;
}

ll N;
vector<ll> A;
void solve() {
  ll XOR = 0;
  ll cnt = 0;
  rep(i, N) XOR ^= A[i];
  if (XOR == 0) {
    ll x = 0;
    vector<ll> B;
    ll now = 0;
    rep(i, N) {
      now ^= A[i];
      B.pb(now);
      if (now == 0) {
        add(i, 1);
        cnt++;
      }
    }
    compress(B);
    ll X = *max_element(B.begin(), B.end());
    vector<ll> L[X + 1];
    rep(i, N) {
      if (B[i] == 0)
        continue;
      L[B[i]].pb(i);
    }
    rep(i, X + 1) L[i].pb(N_);
    mint ans = 0;
    for (ll i = 1; i <= X; i++) {
      if (L[i].size() == 1)
        continue;
      mint s = 0, t = 1;
      for (ll j = 0; j < L[i].size() - 1; j++) {
        ll x = get_sum(L[i][j], L[i][j + 1]);
        s += t;
        t += s * x;
      }
      ans += s;
    }
    ans += pow_mod(2, cnt - 1);
    ans.get();
  } else {
    ll a = XOR;
    ll b = 0;
    ll now = 0;
    mint s = 0, t = 1;
    rep(i, N - 1) {
      now ^= A[i];
      if (now == a) {
        s += t;
      } else if (now == b) {
        t += s;
      }
    }
    t.get();
  }
}

int main() {
  cin >> N;
  A.resize(N);
  rep(i, N) cin >> A[i];
  solve();
}