Problem p02585 (C++)

Buggy submission (status: Runtime Error):
/*input
5 2
2 4 5 1 3
3 4 -10 -8 8

*/

/*
                                                    ______________
                                                          |       )
                                                          |   )   /
                                                          |______/
                                                    |     |      \
                                                    |     |   )   \
                                                    |_____|_______)

*/
#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef long double ld;

#define pb push_back
#define all(c) c.begin(), c.end()
#define allr(c) c.rbegin(), c.rend()
int mod = 1000000007;
const int inf = 1034567891;
const ll LL_INF = 1234567890123456789ll;
#define PI 3.14159265
#define endl '\n'
#define F first
#define S second
#define debug(x) cout << #x << " = " << x << endl;
#define TRACE

#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char *name, Arg1 &&arg1) {
  cout << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names + 1, ',');
  cout.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
#else
#define trace(...)
#endif

#define out(container)                                                         \
  for (auto it : container)                                                    \
    cout << it << " ";                                                         \
  cout << endl;

template <typename T> T GCD(T a, T b) {
  ll t;
  while (a) {
    t = a;
    a = b % a;
    b = t;
  }
  return b;
}
template <typename T> string toString(T a) { return to_string(a); }
template <typename T> void toInt(string s, T &x) {
  stringstream str(s);
  str >> x;
}
inline int add(int x, int y) {
  x += y;
  if (x >= mod)
    x -= mod;
  return x;
}
inline int sub(int x, int y) {
  x -= y;
  if (x < 0)
    x += mod;
  return x;
}
inline int mul(int x, int y) { return (x * 1ll * y) % mod; }
inline int powr(int a, ll b) {
  int x = 1 % mod;
  while (b) {
    if (b & 1)
      x = mul(x, a);
    a = mul(a, a);
    b >>= 1;
  }
  return x;
}
inline int inv(int a) { return powr(a, mod - 2); }

const int N = 5e3 + 5;

int p[N], c[N];

bool vis[N];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  int n, k;
  cin >> n >> k;

  for (int i = 1; i <= n; i++) {
    cin >> p[i];
  }

  ll ans = -LL_INF;

  for (int i = 1; i <= n; i++) {
    cin >> c[i];
    ans = max(ans, (ll)c[i]);
  }

  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      vis[j] = false;
    }
    int cc = i;
    vector<long long> vec;

    vec.push_back(0);

    int m = 0;

    while (!vis[cc]) {
      vis[cc] = true;
      long long x = vec.back();
      vec.push_back(x + c[p[cc]]);
      cc = p[cc];
      m++;
    }

    // out(vec);

    ll cur = 0, mx = -LL_INF;

    for (int j = 1; j <= k; j++) {
      mx = max(mx, vec[j]);
    }

    ans = max(ans, mx);

    ll d = k / m, r = k % m;

    cur += d * vec[m];

    if (d)
      ans = max(ans, cur);

    mx = -LL_INF;

    for (int j = 1; j <= r; j++) {
      mx = max(mx, vec[j]);
    }

    cur += mx;

    ans = max(ans, cur);

    if (d > 0) {
      d--;
      cur = d * vec[m];
      mx = *max_element(vec.begin() + 1, vec.end());
      cur += mx;
      ans = max(ans, cur);
    }
  }

  cout << ans << endl;

  return 0;
}

Fixed submission:
/*input
5 2
2 4 5 1 3
3 4 -10 -8 8

*/

/*
                                                    ______________
                                                          |       )
                                                          |   )   /
                                                          |______/
                                                    |     |      \
                                                    |     |   )   \
                                                    |_____|_______)

*/
#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef long double ld;

#define pb push_back
#define all(c) c.begin(), c.end()
#define allr(c) c.rbegin(), c.rend()
int mod = 1000000007;
const int inf = 1034567891;
const ll LL_INF = 1234567890123456789ll;
#define PI 3.14159265
#define endl '\n'
#define F first
#define S second
#define debug(x) cout << #x << " = " << x << endl;
#define TRACE

#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char *name, Arg1 &&arg1) {
  cout << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names + 1, ',');
  cout.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
#else
#define trace(...)
#endif

#define out(container)                                                         \
  for (auto it : container)                                                    \
    cout << it << " ";                                                         \
  cout << endl;

template <typename T> T GCD(T a, T b) {
  ll t;
  while (a) {
    t = a;
    a = b % a;
    b = t;
  }
  return b;
}
template <typename T> string toString(T a) { return to_string(a); }
template <typename T> void toInt(string s, T &x) {
  stringstream str(s);
  str >> x;
}
inline int add(int x, int y) {
  x += y;
  if (x >= mod)
    x -= mod;
  return x;
}
inline int sub(int x, int y) {
  x -= y;
  if (x < 0)
    x += mod;
  return x;
}
inline int mul(int x, int y) { return (x * 1ll * y) % mod; }
inline int powr(int a, ll b) {
  int x = 1 % mod;
  while (b) {
    if (b & 1)
      x = mul(x, a);
    a = mul(a, a);
    b >>= 1;
  }
  return x;
}
inline int inv(int a) { return powr(a, mod - 2); }

const int N = 5e3 + 5;

int p[N], c[N];

bool vis[N];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  int n, k;
  cin >> n >> k;

  for (int i = 1; i <= n; i++) {
    cin >> p[i];
  }

  ll ans = -LL_INF;

  for (int i = 1; i <= n; i++) {
    cin >> c[i];
    ans = max(ans, (ll)c[i]);
  }

  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      vis[j] = false;
    }
    int cc = i;
    vector<long long> vec;

    vec.push_back(0);

    int m = 0;

    while (!vis[cc]) {
      vis[cc] = true;
      long long x = vec.back();
      vec.push_back(x + c[p[cc]]);
      cc = p[cc];
      m++;
    }

    // out(vec);

    ll cur = 0, mx = -LL_INF;

    for (int j = 1; j <= min(k, m); j++) {
      mx = max(mx, vec[j]);
    }

    ans = max(ans, mx);

    ll d = k / m, r = k % m;

    cur += d * vec[m];

    if (d)
      ans = max(ans, cur);

    mx = -LL_INF;

    for (int j = 1; j <= r; j++) {
      mx = max(mx, vec[j]);
    }

    cur += mx;

    ans = max(ans, cur);

    if (d > 0) {
      d--;
      cur = d * vec[m];
      mx = *max_element(vec.begin() + 1, vec.end());
      cur += mx;
      ans = max(ans, cur);
    }
  }

  cout << ans << endl;

  return 0;
}