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

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int maxn = 3010;

int a[maxn][maxn];
bool vis[maxn];
ll dp[3005][3005][4];

int main() {
  int n, m, k;
  cin >> n >> m >> k;

  for (int i = 1; i <= k; i++) {
    int x, y, w;
    cin >> x >> y >> w;
    a[x][y] = w;
  }

  dp[1][1][1] = a[1][1];
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      if (i == 1 && j == 1)
        continue;

      ll maxup =
          max(dp[i - 1][j][3],
              max(dp[i - 1][j][2], max(dp[i - 1][j][1], dp[i - 1][j][0])));
      dp[i][j][0] = max(maxup, dp[i - 1][j][0]);
      for (int k = 1; k <= 3; k++) {
        dp[i][j][k] = max(dp[i][j - 1][k - 1] + a[i][j], dp[i][j - 1][k]);
      }
      dp[i][j][1] = max(maxup + a[i][j], dp[i][j][1]);
    }
  }
  ll ans = max(dp[n][m][0], max(dp[n][m][1], max(dp[n][m][2], dp[n][m][3])));
  cout << ans << endl;
}

Error: -11

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <tuple>
#include <utility>
#include <vector>
#define ll long long
#define itn int
#define endl '\\n'
#define co(ans) cout << ans << endl
#define COYE cout << "YES" << endl
#define COYe cout << "Yes" << endl
#define COye cout << "yes" << endl
#define CONO cout << "NO" << endl
#define CONo cout << "No" << endl
#define COno cout << "no" << endl
#define FORE(i, a) for (auto &i : a)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FFOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define RREP(i, n) FFOR(i, 1, n)
#define PB push_back
#define MP make_pair
#define ALL(V) (V).begin(), (V).end()
#define SORT(V) sort((V).begin(), (V).end())
#define REVERSE(V) reverse((V).begin(), (V).end())
#define EACH(V, i)                                                             \\
  for (typeof((V).begin()) i = (V).begin(); i != (V).end(); ++i)
#define equals(a, b) (fabs((a) - (b)) < EPS)
#define INF ((1LL << 62) - (1LL << 31))
#define EPS 1e-10
#define PI 3.141592653589793238
#define MOD 1000000007
#define MAX 5100000
using namespace std;
using Edge = pair<ll, ll>;
using Graph = vector<vector<int>>;
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
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 (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
const int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

int main() {
  ll R, C, K;
  cin >> R >> C >> K;

  ll DP[3002][3002][4], L[3002][3002];
  for (int i = 0; i <= 3001; ++i) {
    for (int j = 0; j <= 3001; ++j) {
      L[i][j] = -1;
      for (int k = 0; k < 4; ++k) {
        DP[i][j][k] = 0;
      }
    }
  }

  ll RR[K], CC[K], VV[K];
  REP(i, K) {
    cin >> RR[i] >> CC[i] >> VV[i];
    L[RR[i]][CC[i]] = VV[i];
  }

  for (int i = 1; i <= 3001; ++i) {
    for (int j = 1; j <= 3001; ++j) {
      for (int k = 0; k < 4; ++k) {
        if (L[i][j] != -1) {
          if (k < 3)
            chmax(DP[i][j][k + 1], DP[i][j - 1][k] + L[i][j]);
          chmax(DP[i][j][1], DP[i - 1][j][k] + L[i][j]);
        }
        chmax(DP[i][j][k], DP[i][j - 1][k]);
        chmax(DP[i][j][0], DP[i - 1][j][k]);
      }
    }
  }

  cout << DP[3001][3001][0] << endl;
  return 0;
}