Problem p02586 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
#define rep(i, n) for (long long int i = 0; i < n; i++)
#define _rep(i, m, n) for (long long int i = m; i < n; i++)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
const ll mod = 1000000007;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

ll gcd(ll A, ll B) {
  if (B == 0)
    return A;
  return gcd(B, A % B);
}
ll lcm(ll A, ll B) { return A * B / gcd(A, B); }
template <typename T> T pow(T a, ll n, T e = 1) {
  T ret = e;
  while (n) {
    if (n & 1)
      ret *= a;
    a *= a;
    n >>= 1;
  }
  return ret;
}

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long x_) {
    if ((x = x_ % mod + mod) >= mod)
      x -= mod;
  }
  ModInt &operator+=(ModInt rhs) {
    if ((x += rhs.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(ModInt rhs) {
    if ((x -= rhs.x) < 0)
      x += mod;
    return *this;
  }
  ModInt &operator*=(ModInt rhs) {
    x = (unsigned long long)x * rhs.x % mod;
    return *this;
  }
  ModInt &operator/=(ModInt rhs) {
    x = (unsigned long long)x * rhs.inv().x % mod;
    return *this;
  }

  ModInt operator-() const { return -x < 0 ? mod - x : -x; }
  ModInt operator+(ModInt rhs) const { return ModInt(*this) += rhs; }
  ModInt operator-(ModInt rhs) const { return ModInt(*this) -= rhs; }
  ModInt operator*(ModInt rhs) const { return ModInt(*this) *= rhs; }
  ModInt operator/(ModInt rhs) const { return ModInt(*this) /= rhs; }
  bool operator==(ModInt rhs) const { return x == rhs.x; }
  bool operator!=(ModInt rhs) const { return x != rhs.x; }
  ModInt inv() const { return pow(*this, mod - 2); }

  friend ostream &operator<<(ostream &s, ModInt<mod> a) {
    s << a.x;
    return s;
  }
  friend istream &operator>>(istream &s, ModInt<mod> &a) {
    s >> a.x;
    return s;
  }
};

using mint = ModInt<1000000007>;
using Graph = vector<vector<int>>;
Graph G;
/*------------------------------------------------------------------*/
ll dp[3000][3000][4];
ll score[3000][3000];
int main() {
  ll R, C, K;
  cin >> R >> C >> K;

  rep(i, R + 1) rep(j, C + 1) score[i][j] = 0;
  rep(i, K) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    score[a][b] = c;
  }
  rep(i, 3000) rep(j, 3000) rep(k, 4) dp[i][j][k] = 0;
  if (score[0][0] > 0)
    dp[0][0][1] = score[0][0];

  rep(i, R) rep(j, C) rep(k, 4) {
    if (j + 1 < C) {
      dp[i][j + 1][k] = max(dp[i][j][k], dp[i][j + 1][k]);
      if (k < 3)
        dp[i][j + 1][k + 1] =
            max(dp[i][j][k] + score[i][j + 1], dp[i][j + 1][k + 1]);
    }
    if (i + 1 < R) {
      dp[i + 1][j][0] = max(dp[i][j][k], dp[i + 1][j][0]);
      dp[i + 1][j][1] = max(dp[i][j][k] + score[i + 1][j], dp[i + 1][j][1]);
    }
  }
  ll ans_max = 0;
  rep(k, 4) ans_max = max(ans_max, dp[R - 1][C - 1][k]);
  cout << ans_max << endl;
}

Error: -11

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (long long int i = 0; i < n; i++)
#define _rep(i, m, n) for (long long int i = m; i < n; i++)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
const ll mod = 1000000007;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

ll gcd(ll A, ll B) {
  if (B == 0)
    return A;
  return gcd(B, A % B);
}
ll lcm(ll A, ll B) { return A * B / gcd(A, B); }
template <typename T> T pow(T a, ll n, T e = 1) {
  T ret = e;
  while (n) {
    if (n & 1)
      ret *= a;
    a *= a;
    n >>= 1;
  }
  return ret;
}

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long x_) {
    if ((x = x_ % mod + mod) >= mod)
      x -= mod;
  }
  ModInt &operator+=(ModInt rhs) {
    if ((x += rhs.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(ModInt rhs) {
    if ((x -= rhs.x) < 0)
      x += mod;
    return *this;
  }
  ModInt &operator*=(ModInt rhs) {
    x = (unsigned long long)x * rhs.x % mod;
    return *this;
  }
  ModInt &operator/=(ModInt rhs) {
    x = (unsigned long long)x * rhs.inv().x % mod;
    return *this;
  }

  ModInt operator-() const { return -x < 0 ? mod - x : -x; }
  ModInt operator+(ModInt rhs) const { return ModInt(*this) += rhs; }
  ModInt operator-(ModInt rhs) const { return ModInt(*this) -= rhs; }
  ModInt operator*(ModInt rhs) const { return ModInt(*this) *= rhs; }
  ModInt operator/(ModInt rhs) const { return ModInt(*this) /= rhs; }
  bool operator==(ModInt rhs) const { return x == rhs.x; }
  bool operator!=(ModInt rhs) const { return x != rhs.x; }
  ModInt inv() const { return pow(*this, mod - 2); }

  friend ostream &operator<<(ostream &s, ModInt<mod> a) {
    s << a.x;
    return s;
  }
  friend istream &operator>>(istream &s, ModInt<mod> &a) {
    s >> a.x;
    return s;
  }
};

using mint = ModInt<1000000007>;
using Graph = vector<vector<int>>;
Graph G;
/*------------------------------------------------------------------*/
ll dp[3000][3000][4];
ll score[3000][3000];
int main() {
  ll R, C, K;
  cin >> R >> C >> K;

  rep(i, R + 1) rep(j, C + 1) score[i][j] = 0;
  rep(i, K) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    score[a][b] = c;
  }
  rep(i, 3000) rep(j, 3000) rep(k, 4) dp[i][j][k] = 0;
  if (score[0][0] > 0)
    dp[0][0][1] = score[0][0];

  rep(i, R) rep(j, C) rep(k, 4) {
    if (k < 3) {
      dp[i][j + 1][k + 1] =
          max(dp[i][j][k] + score[i][j + 1], dp[i][j + 1][k + 1]);
    }
    dp[i][j + 1][k] = max(dp[i][j][k], dp[i][j + 1][k]);
    dp[i + 1][j][0] = max(dp[i][j][k], dp[i + 1][j][0]);
    dp[i + 1][j][1] = max(dp[i][j][k] + score[i + 1][j], dp[i + 1][j][1]);
  }
  ll ans_max = 0;
  rep(k, 4) ans_max = max(ans_max, dp[R - 1][C - 1][k]);
  cout << ans_max << endl;
}