Problem p03128 (C++)

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

using namespace std;

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define DEBUG_VEC(v)                                                           \
  cerr << #v << ":";                                                           \
  for (int i = 0; i < v.size(); i++)                                           \
    cerr << " " << v[i];                                                       \
  cerr << endl
#define DEBUG_MAT(v)                                                           \
  cerr << #v << endl;                                                          \
  for (int i = 0; i < v.size(); i++) {                                         \
    for (int j = 0; j < v[i].size(); j++) {                                    \
      cerr << v[i][j] << " ";                                                  \
    }                                                                          \
    cerr << endl;                                                              \
  }

typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector<vector<int>>
#define vll vector<vector<ll>>
#define vs vector<string>
#define pii pair<int, int>
#define pis pair<int, string>
#define psi pair<string, int>
#define pll pair<ll, ll>
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T> ostream &operator<<(ostream &os, pair<S, T> p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}
#define X first
#define Y second
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define rrep1(i, n) for (int i = (n); i > 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(), c.end()
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const ll MOD = 1000000007;
// const ll MOD = 998244353;
const double pi = 3.14159265358979323846;
#define Sp(p) cout << setprecision(15) << fixed << p << endl;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
int dx2[8] = {1, 1, 0, -1, -1, -1, 0, 1}, dy2[8] = {0, 1, 1, 1, 0, -1, -1, -1};
#define fio()                                                                  \
  cin.tie(0);                                                                  \
  ios::sync_with_stdio(false);
// #define mp make_pair
vector<vector<bool>> dp(10001, vector<bool>(5001));

int main() {
  int n, m;
  cin >> n >> m;
  vi use = {0, 2, 5, 5, 4, 5, 6, 3, 7, 6};
  vi a(m);
  rep(i, m) { cin >> a[i]; }
  sort(all(a));
  dp[0][0] = 1;
  rep(i, n) {
    rep(j, 5001) {
      if (!dp[i][j])
        continue;
      rep(k, m) {
        int add = use[a[k]];
        dp[i + add][j + 1] = true;
      }
    }
  }
  int keta;
  for (keta = 5000; keta >= 0; keta--) {
    if (dp[n][keta])
      break;
  }
  string ans;
  while (n > 0) {
    rrep(i, m) {
      int add = use[a[i]];
      if (n < add)
        continue;
      if (dp[n - add][keta - 1]) {
        ans.push_back(a[i] + '0');
        keta--;
        n -= add;
        break;
      }
    }
  }
  cout << ans << endl;
}


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

using namespace std;

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define DEBUG_VEC(v)                                                           \
  cerr << #v << ":";                                                           \
  for (int i = 0; i < v.size(); i++)                                           \
    cerr << " " << v[i];                                                       \
  cerr << endl
#define DEBUG_MAT(v)                                                           \
  cerr << #v << endl;                                                          \
  for (int i = 0; i < v.size(); i++) {                                         \
    for (int j = 0; j < v[i].size(); j++) {                                    \
      cerr << v[i][j] << " ";                                                  \
    }                                                                          \
    cerr << endl;                                                              \
  }

typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector<vector<int>>
#define vll vector<vector<ll>>
#define vs vector<string>
#define pii pair<int, int>
#define pis pair<int, string>
#define psi pair<string, int>
#define pll pair<ll, ll>
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T> ostream &operator<<(ostream &os, pair<S, T> p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}
#define X first
#define Y second
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define rrep1(i, n) for (int i = (n); i > 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(), c.end()
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const ll MOD = 1000000007;
// const ll MOD = 998244353;
const double pi = 3.14159265358979323846;
#define Sp(p) cout << setprecision(15) << fixed << p << endl;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
int dx2[8] = {1, 1, 0, -1, -1, -1, 0, 1}, dy2[8] = {0, 1, 1, 1, 0, -1, -1, -1};
#define fio()                                                                  \
  cin.tie(0);                                                                  \
  ios::sync_with_stdio(false);
// #define mp make_pair
vector<vector<bool>> dp(10001, vector<bool>(5001));

int main() {
  int n, m;
  cin >> n >> m;
  vi use = {0, 2, 5, 5, 4, 5, 6, 3, 7, 6};
  vi a(m);
  rep(i, m) { cin >> a[i]; }
  sort(all(a));
  dp[0][0] = 1;
  rep(i, n) {
    rep(j, 5001) {
      if (!dp[i][j])
        continue;
      rep(k, m) {
        int add = use[a[k]];
        if (i + add > n)
          continue;
        dp[i + add][j + 1] = true;
      }
    }
  }
  int keta;
  for (keta = 5000; keta >= 0; keta--) {
    if (dp[n][keta])
      break;
  }
  string ans;
  while (n > 0) {
    rrep(i, m) {
      int add = use[a[i]];
      if (n < add)
        continue;
      if (dp[n - add][keta - 1]) {
        ans.push_back(a[i] + '0');
        keta--;
        n -= add;
        break;
      }
    }
  }
  cout << ans << endl;
}