Problem p03137 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <complex>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

#define REP(i, m, n) for (int i = int(m); i < int(n); i++)
#define RREP(i, m, n) for (int i = int(n) - 1; i >= int(m); --i)
#define EACH(i, c) for (auto &(i) : c)
#define all(c) begin(c), end(c)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort(begin(c), end(c))
#define pb emplace_back
#define MP make_pair
#define SZ(a) int((a).size())

#ifdef LOCAL
#define DEBUG(s) cout << (s) << endl
#define dump(x) cerr << #x << " = " << (x) << endl
#define BR cout << endl;
#else
#define DEBUG(s)                                                               \
  do {                                                                         \
  } while (0)
#define dump(x)                                                                \
  do {                                                                         \
  } while (0)
#define BR
#endif
using namespace std;

using UI = unsigned int;
using UL = unsigned long;
using LL = long long int;
using ULL = unsigned long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VLL = vector<LL>;
using VS = vector<string>;
using PII = pair<int, int>;
using VP = vector<PII>;

// struct edge {int from, to, cost;};

constexpr double EPS = 1e-10;
// constexpr double PI  = acos(-1.0);
// constexpr int INF = INT_MAX;
constexpr int MOD = 1'000'000'007;
// inline void modAdd(LL &l, LL &r) {l = (l + r) % MOD;}

template <class T> inline T sqr(T x) { return x * x; }

void solve() {
  int n, m;
  cin >> n >> m;
  VI x(m);
  REP(i, 0, m) cin >> x[i];
  REP(i, 0, m) x[i] += 100000;
  sort(all(x));
  if (m == 1) {
    cout << 0 << endl;
    return;
  }
  int sum = 0;
  VI ds(m - 1);
  REP(i, 0, m - 1) {
    int d = x[i + 1] - x[i];
    sum += d;
    ds[i] = d;
  }
  sort(all(ds));
  reverse(all(ds));
  REP(i, 0, n - 1) sum -= ds[i];
  cout << sum << endl;
}

int main() {
  solve();

  return 0;
}

Fixed submission:
#include <algorithm>
#include <complex>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

#define REP(i, m, n) for (int i = int(m); i < int(n); i++)
#define RREP(i, m, n) for (int i = int(n) - 1; i >= int(m); --i)
#define EACH(i, c) for (auto &(i) : c)
#define all(c) begin(c), end(c)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort(begin(c), end(c))
#define pb emplace_back
#define MP make_pair
#define SZ(a) int((a).size())

#ifdef LOCAL
#define DEBUG(s) cout << (s) << endl
#define dump(x) cerr << #x << " = " << (x) << endl
#define BR cout << endl;
#else
#define DEBUG(s)                                                               \
  do {                                                                         \
  } while (0)
#define dump(x)                                                                \
  do {                                                                         \
  } while (0)
#define BR
#endif
using namespace std;

using UI = unsigned int;
using UL = unsigned long;
using LL = long long int;
using ULL = unsigned long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VLL = vector<LL>;
using VS = vector<string>;
using PII = pair<int, int>;
using VP = vector<PII>;

// struct edge {int from, to, cost;};

constexpr double EPS = 1e-10;
// constexpr double PI  = acos(-1.0);
// constexpr int INF = INT_MAX;
constexpr int MOD = 1'000'000'007;
// inline void modAdd(LL &l, LL &r) {l = (l + r) % MOD;}

template <class T> inline T sqr(T x) { return x * x; }

void solve() {
  int n, m;
  cin >> n >> m;
  VI x(m);
  REP(i, 0, m) cin >> x[i];
  REP(i, 0, m) x[i] += 100000;
  sort(all(x));
  if (m == 1 || n >= m) {
    cout << 0 << endl;
    return;
  }
  int sum = 0;
  VI ds(m - 1);
  REP(i, 0, m - 1) {
    int d = x[i + 1] - x[i];
    sum += d;
    ds[i] = d;
  }
  sort(all(ds));
  reverse(all(ds));
  REP(i, 0, n - 1) sum -= ds[i];
  cout << sum << endl;
}

int main() {
  solve();

  return 0;
}