Problem p03032 (C++)

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

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

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

#define DEBUG(x) cout << #x << ": " << (x) << '\n'
#define DEBUG_VEC(v)                                                           \
  cout << #v << ":";                                                           \
  REP(i, v.size()) cout << ' ' << v[i];                                        \
  cout << '\n'
#define ALL(a) (a).begin(), (a).end()

template <typename T> inline void CHMAX(T &a, const T b) {
  if (a < b)
    a = b;
}
template <typename T> inline void CHMIN(T &a, const T b) {
  if (a > b)
    a = b;
}

constexpr ll MOD = 1000000007ll;
// constexpr ll MOD=998244353ll;
#define FIX(a) ((a) % MOD + MOD) % MOD

const double EPS = 1e-11;
#define EQ0(x) (abs((x)) < EPS)
#define EQ(a, b) (abs((a) - (b)) < EPS)

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout<<setprecision(10)<<fixed;
  int n, k;
  int v[60];
  cin >> n >> k;
  assert(n > 50 || k > 100);
  REP(i, n) { cin >> v[i]; }
  int ans = 0;
  REP(i, k + 1) {
    REP(j, k - i + 1) {
      if (i + j > n) {
        continue;
      }
      int x2[i + j];
      REP(j2, i) { x2[j2] = v[j2]; }
      int cnt = i - 1;
      FORR(j2, n - j, n) { x2[++cnt] = v[j2]; }
      sort(x2, x2 + i + j);
      int sum = 0;
      REP(a, i + j) { sum += x2[a]; }
      REP(a, min(k - i - j, i + j)) {
        if (x2[a] >= 0) {
          break;
        }
        sum -= x2[a];
      }
      CHMAX(ans, sum);
    }
  }
  cout << ans << '\n';
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

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

#define DEBUG(x) cout << #x << ": " << (x) << '\n'
#define DEBUG_VEC(v)                                                           \
  cout << #v << ":";                                                           \
  REP(i, v.size()) cout << ' ' << v[i];                                        \
  cout << '\n'
#define ALL(a) (a).begin(), (a).end()

template <typename T> inline void CHMAX(T &a, const T b) {
  if (a < b)
    a = b;
}
template <typename T> inline void CHMIN(T &a, const T b) {
  if (a > b)
    a = b;
}

constexpr ll MOD = 1000000007ll;
// constexpr ll MOD=998244353ll;
#define FIX(a) ((a) % MOD + MOD) % MOD

const double EPS = 1e-11;
#define EQ0(x) (abs((x)) < EPS)
#define EQ(a, b) (abs((a) - (b)) < EPS)

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout<<setprecision(10)<<fixed;
  int n, k;
  int v[60];
  cin >> n >> k;
  assert(n <= 50 || k <= 100);
  REP(i, n) { cin >> v[i]; }
  int ans = 0;
  REP(i, k + 1) {
    REP(j, k - i + 1) {
      if (i + j > n) {
        continue;
      }
      int x2[i + j];
      REP(j2, i) { x2[j2] = v[j2]; }
      int cnt = i - 1;
      FORR(j2, n - j, n) { x2[++cnt] = v[j2]; }
      sort(x2, x2 + i + j);
      int sum = 0;
      REP(a, i + j) { sum += x2[a]; }
      REP(a, min(k - i - j, i + j)) {
        if (x2[a] >= 0) {
          break;
        }
        sum -= x2[a];
      }
      CHMAX(ans, sum);
    }
  }
  cout << ans << '\n';
  return 0;
}