Problem p02935 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define rep(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rrep(i, a, b) for (int i = (int)(a); i >= (int)(b); --i)
#define fore(i, a) for (auto &i : a)
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define isin(i, a, b) ((a) <= (i) && (i) <= (b))
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define fi first
#define se second
#define pb push_back
#define v(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
using ll = long long;
using vi = vector<int>;
using unit = unsigned;
using vl = vector<ll>;
using ull = unsigned long long;
using vvi = vector<vi>;
using P = pair<int, int>;
using vvl = vector<vl>;
using vp = vector<P>;
void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  _main();
}
template <class T> string join(const v(T) & v) {
  stringstream s;
  rep(i, 0, sz(v)) s << ' ' << v[i];
  return s.str().substr(1);
}
template <class T> istream &operator>>(istream &i, v(T) & v) {
  fore(x, v) { i >> v; }
  return i;
}
template <class T> ostream &operator<<(ostream &o, const v(T) & v) {
  o << "[";
  fore(x, v) o << x << ",";
  o << "]";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const deque<T> &v) {
  o << "deq[";
  fore(x, v) o << x << ",";
  o << "]";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const set<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const unordered_set<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const multiset<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T>
ostream &operator<<(ostream &o, const unordered_multiset<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T1, class T2>
ostream &operator<<(ostream &o, const pair<T1, T2> &p) {
  o << "(" << p.fi << "," << p.se << ")";
  return o;
}
template <class TK, class TV>
ostream &operator<<(ostream &o, const map<TK, TV> &m) {
  o << "{";
  fore(x, m) o << x.fi << "=>" << x.se << ",";
  o << "}";
  return o;
}
template <class TK, class TV>
ostream &operator<<(ostream &o, const unordered_map<TK, TV> &m) {
  o << "{";
  fore(x, m) o << x.fi << "=>" << x.se << ",";
  o << "}";
  return o;
}
template <class T> void YES(T c) {
  if (c)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
template <class T> void Yes(T c) {
  if (c)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
template <class T> void POSS(T c) {
  if (c)
    cout << "POSSIBLE" << endl;
  else
    cout << "IMPOSSIBLE" << endl;
}
template <class T> void Poss(T c) {
  if (c)
    cout << "Possible" << endl;
  else
    cout << "Impossible" << endl;
}
template <class T> void chmax(T &a, const T &b) {
  if (a < b)
    a = b;
}
template <class T> void chmin(T &a, const T &b) {
  if (b < a)
    a = b;
}
template <class T> T gcd(T a, T b) { return (b == 0) ? a : gcd(b, a % b); }
template <class T> T lcm(T a, T b) { return a * (b / gcd(a, b)); }
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = INT_MAX / 2;
const ll INFL = 1LL << 60;
const int dx[] = {-1, 0, 1, 0, -1, -1, 1, 1};
const int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

void _main() {
  int N;
  cin >> N;
  v(double) V(N);
  fore(x, V) cin >> x;
  vi idx(N);
  iota(all(idx), 0);

  double ans = 0;
  do {
    double tmp = (V[idx[0]] + V[idx[1]]) / 2.0;
    rep(i, 2, N) { tmp = (tmp + V[idx[i]]) / 2.0; }
    chmax(ans, tmp);
  } while (next_permutation(all(idx)));

  cout << ans << endl;
}

Fixed submission:
#include <bits/stdc++.h>
#define rep(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rrep(i, a, b) for (int i = (int)(a); i >= (int)(b); --i)
#define fore(i, a) for (auto &i : a)
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define isin(i, a, b) ((a) <= (i) && (i) <= (b))
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define fi first
#define se second
#define pb push_back
#define v(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
using ll = long long;
using vi = vector<int>;
using unit = unsigned;
using vl = vector<ll>;
using ull = unsigned long long;
using vvi = vector<vi>;
using P = pair<int, int>;
using vvl = vector<vl>;
using vp = vector<P>;
void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  _main();
}
template <class T> string join(const v(T) & v) {
  stringstream s;
  rep(i, 0, sz(v)) s << ' ' << v[i];
  return s.str().substr(1);
}
template <class T> istream &operator>>(istream &i, v(T) & v) {
  fore(x, v) { i >> v; }
  return i;
}
template <class T> ostream &operator<<(ostream &o, const v(T) & v) {
  o << "[";
  fore(x, v) o << x << ",";
  o << "]";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const deque<T> &v) {
  o << "deq[";
  fore(x, v) o << x << ",";
  o << "]";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const set<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const unordered_set<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const multiset<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T>
ostream &operator<<(ostream &o, const unordered_multiset<T> &v) {
  o << "{";
  fore(x, v) o << x << ",";
  o << "}";
  return o;
}
template <class T1, class T2>
ostream &operator<<(ostream &o, const pair<T1, T2> &p) {
  o << "(" << p.fi << "," << p.se << ")";
  return o;
}
template <class TK, class TV>
ostream &operator<<(ostream &o, const map<TK, TV> &m) {
  o << "{";
  fore(x, m) o << x.fi << "=>" << x.se << ",";
  o << "}";
  return o;
}
template <class TK, class TV>
ostream &operator<<(ostream &o, const unordered_map<TK, TV> &m) {
  o << "{";
  fore(x, m) o << x.fi << "=>" << x.se << ",";
  o << "}";
  return o;
}
template <class T> void YES(T c) {
  if (c)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
template <class T> void Yes(T c) {
  if (c)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
template <class T> void POSS(T c) {
  if (c)
    cout << "POSSIBLE" << endl;
  else
    cout << "IMPOSSIBLE" << endl;
}
template <class T> void Poss(T c) {
  if (c)
    cout << "Possible" << endl;
  else
    cout << "Impossible" << endl;
}
template <class T> void chmax(T &a, const T &b) {
  if (a < b)
    a = b;
}
template <class T> void chmin(T &a, const T &b) {
  if (b < a)
    a = b;
}
template <class T> T gcd(T a, T b) { return (b == 0) ? a : gcd(b, a % b); }
template <class T> T lcm(T a, T b) { return a * (b / gcd(a, b)); }
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = INT_MAX / 2;
const ll INFL = 1LL << 60;
const int dx[] = {-1, 0, 1, 0, -1, -1, 1, 1};
const int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

void _main() {
  int N;
  cin >> N;
  v(double) V(N);
  fore(x, V) cin >> x;
  sort(all(V));
  double ans = (V[0] + V[1]) / 2.0;
  rep(i, 2, N) { ans = (ans + V[i]) / 2.0; }
  cout << ans << endl;
}