Problem p02585 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 60;

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

ll gcd(ll n, ll m) {
  ll tmp;
  while (m != 0) {
    tmp = n % m;
    n = m;
    m = tmp;
  }
  return n;
}

ll lcm(ll n, ll m) {
  return abs(n) / gcd(n, m) * abs(m); // gl=xy
}

using namespace std;

void solve() {
  ll n, k;
  cin >> n >> k;
  vector<ll> p(n), c(n);
  rep(i, n) cin >> p[i], p[i]--;
  rep(i, n) cin >> c[i];
  ll ans = -INF;
  rep(i, n) {
    vector<bool> used(n);
    ll s = i;
    ll nx = s;
    ll cnt = k;
    ll loop = 1;
    ll res = 0;
    while (cnt > 0) {
      nx = p[nx];
      if (used[nx]) {
        loop = k - cnt;
        break;
      }
      res += c[nx];
      chmax(ans, res);
      --cnt;
      used[nx] = true;
    }
    if (cnt > 0) {
      if (cnt / loop - 1 >= 0 && res > 0) {
        res += (cnt / loop - 1) * res;
        cnt %= loop;
        cnt += loop;
      }
      chmax(ans, res);
      loop *= 2;
      loop += 5;
      while (cnt > 0 && loop > 0) {
        res += c[nx];
        chmax(ans, res);
        nx = p[nx];
        --cnt;
        --loop;
      }
    }
  }
  cout << ans;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 60;

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

ll gcd(ll n, ll m) {
  ll tmp;
  while (m != 0) {
    tmp = n % m;
    n = m;
    m = tmp;
  }
  return n;
}

ll lcm(ll n, ll m) {
  return abs(n) / gcd(n, m) * abs(m); // gl=xy
}

using namespace std;

void solve() {
  ll n, k;
  cin >> n >> k;
  vector<ll> p(n), c(n);
  rep(i, n) cin >> p[i], p[i]--;
  rep(i, n) cin >> c[i];
  ll ans = -INF;
  rep(i, n) {
    vector<bool> used(n);
    int s = i;
    int nx = s;
    int cnt = k;
    int loop = 1;
    ll res = 0;
    while (cnt > 0) {
      nx = p[nx];
      if (used[nx]) {
        loop = k - cnt;
      }
      res += c[nx];
      chmax(ans, res);
      --cnt;
      used[nx] = true;
    }
    if (cnt > 0 && res > 0) {
      if (cnt / loop - 1 >= 0) {
        res += (cnt / loop - 1) * res;
        cnt %= loop;
        cnt += loop;
      }
      loop++;
      while (cnt > 0 && loop > 0) {
        res += c[nx];
        chmax(ans, res);
        nx = p[nx];
        --cnt;
        --loop;
      }
    }
  }
  cout << ans;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}