Problem p02586 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
template <class T> ostream &operator<<(ostream &os, vector<T> V) {
  os << "[ ";
  for (auto v : V)
    os << v << " ";
  return os << "]";
}
template <class T> ostream &operator<<(ostream &os, set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class L, class R> ostream &operator<<(ostream &os, pair<L, R> P) {
  return os << "(" << P.first << "," << P.second << ")";
}
template <class L, class R> ostream &operator<<(ostream &os, map<L, R> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ")";
  return os << "}";
}
#define cerr cout
#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char *name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
#else
#define trace(...) 1
#endif
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
// #define ordered_set tree<int, null_type,less<int>,
// rb_tree_tag,tree_order_statistics_node_update> find_by_order(k)  returns
// iterator to kth element starting from 0; order_of_key(k) returns count of
// elements strictly smaller than k;
// For multiset use less_equal operator but it does support erase operations for
// multiset
#define ll long long
#define ld long double
#define vll vector<ll>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define I insert
#define pb push_back
#define F first
#define S second
#define endl "\n"
#define all(v) (v).begin(), (v).end()
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef pair<pii, int> ppi;
typedef vector<pii> vpii;
#define fio                                                                    \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL);                                                               \
  cout.tie(NULL)
#define mp make_pair

const int mod = 1e9 + 7;

inline int add(int a, int b) {
  a += b;
  if (a >= mod)
    a -= mod;
  return a;
}
inline int sub(int a, int b) {
  a -= b;
  if (a < 0)
    a += mod;
  return a;
}
inline int mul(int a, int b) { return a * 1ll * b % mod; }
inline int power(int x, ll y) {
  int res = 1;
  while (y) {
    if (y & 1)
      res = mul(res, x);
    x = mul(x, x);
    y >>= 1;
  }
  return res;
}
int r, c, k;
const int N = 1e3 + 100;
ll val[N][N];
ll dp[4][N][N];

int main() {
  fio;
  cout << fixed << setprecision(25);
  cin >> r >> c >> k;
  int r1, c1, v1;
  for (int i = 1; i <= k; ++i) {
    cin >> r1 >> c1 >> v1;
    val[r1][c1] = v1;
  }
  for (int i = 1; i <= r; ++i) {
    for (int j = 1; j <= c; ++j) {
      for (int k = 0; k < 4; ++k) {
        dp[0][i][j] = max(dp[0][i][j], dp[k][i - 1][j]);
        dp[1][i][j] = max(dp[1][i][j], val[i][j] + dp[k][i - 1][j]);
        if (k) {
          dp[k][i][j] = max(dp[k][i][j], val[i][j] + dp[k - 1][i][j - 1]);
          dp[k][i][j] = max(dp[k][i][j], dp[k][i][j - 1]);
        }
      }
    }
  }
  ll mx = 0;
  for (int i = 0; i < 4; ++i)
    mx = max(mx, dp[i][r][c]);
  cout << mx << endl;
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
template <class T> ostream &operator<<(ostream &os, vector<T> V) {
  os << "[ ";
  for (auto v : V)
    os << v << " ";
  return os << "]";
}
template <class T> ostream &operator<<(ostream &os, set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class L, class R> ostream &operator<<(ostream &os, pair<L, R> P) {
  return os << "(" << P.first << "," << P.second << ")";
}
template <class L, class R> ostream &operator<<(ostream &os, map<L, R> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ")";
  return os << "}";
}
#define cerr cout
#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char *name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
#else
#define trace(...) 1
#endif
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
// #define ordered_set tree<int, null_type,less<int>,
// rb_tree_tag,tree_order_statistics_node_update> find_by_order(k)  returns
// iterator to kth element starting from 0; order_of_key(k) returns count of
// elements strictly smaller than k;
// For multiset use less_equal operator but it does support erase operations for
// multiset
#define ll long long
#define ld long double
#define vll vector<ll>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define I insert
#define pb push_back
#define F first
#define S second
#define endl "\n"
#define all(v) (v).begin(), (v).end()
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef pair<pii, int> ppi;
typedef vector<pii> vpii;
#define fio                                                                    \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL);                                                               \
  cout.tie(NULL)
#define mp make_pair

const int mod = 1e9 + 7;

inline int add(int a, int b) {
  a += b;
  if (a >= mod)
    a -= mod;
  return a;
}
inline int sub(int a, int b) {
  a -= b;
  if (a < 0)
    a += mod;
  return a;
}
inline int mul(int a, int b) { return a * 1ll * b % mod; }
inline int power(int x, ll y) {
  int res = 1;
  while (y) {
    if (y & 1)
      res = mul(res, x);
    x = mul(x, x);
    y >>= 1;
  }
  return res;
}
int r, c, k;
const int N = 3e3 + 100;
ll val[N][N];
ll dp[4][N][N];

int main() {
  fio;
  cout << fixed << setprecision(25);
  cin >> r >> c >> k;
  int r1, c1, v1;
  for (int i = 1; i <= k; ++i) {
    cin >> r1 >> c1 >> v1;
    val[r1][c1] = v1;
  }
  for (int i = 1; i <= r; ++i) {
    for (int j = 1; j <= c; ++j) {
      for (int k = 0; k < 4; ++k) {
        dp[0][i][j] = max(dp[0][i][j], dp[k][i - 1][j]);
        dp[1][i][j] = max(dp[1][i][j], val[i][j] + dp[k][i - 1][j]);
        if (k) {
          dp[k][i][j] = max(dp[k][i][j], val[i][j] + dp[k - 1][i][j - 1]);
          dp[k][i][j] = max(dp[k][i][j], dp[k][i][j - 1]);
        }
      }
    }
  }
  ll mx = 0;
  for (int i = 0; i < 4; ++i)
    mx = max(mx, dp[i][r][c]);
  cout << mx << endl;
  return 0;
}