Problem p02647 (C++) — buggy submission, verdict: Time Limit Exceeded

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

using ll = long long int;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rrep(i, a, b) for (int i = a; i >= b; i--)
#define fore(i, a) for (auto &i : a)
#define all(x) (x).begin(), (x).end()

#define pi 3.14159265358979323846

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;
}

ll cnt_rep = 0;
ll powmod(ll N, ll P, ll M) {
  cnt_rep++;
  if (P == 0)
    return 1;
  if (P % 2 == 0) {
    ll t = powmod(N, P / 2, M);
    return t * t % M;
  }
  return (N * powmod(N, P - 1, M)) % M;
}

ll gcd(ll a, ll b) {
  ll resi, g, l;
  if (a > b) {
    g = a;
    l = b;
  } else if (b > a) {
    g = b;
    l = a;
  } else {
    return a;
  }
  resi = g % l;
  if (resi != 0) {
    return gcd(l, resi);
  } else {
    return l;
  }
}

template <typename T> void remove(std::vector<T> &vector, unsigned int index) {
  vector.erase(vector.begin() + index);
}

int ans = 0;
int N, M, Q;

template <typename T> void showall(vector<T> v) {
  rep(i, 0, v.size()) { cout << v[i] << " "; }
  cout << endl;
}

template <typename T> ll com(T n, T m, T mod) {
  ll a = 1, b = 1, ans;
  if (n == m || m == 0) {
    ans = 1;
  } else {
    for (ll i = 0; i < m; i++) {
      a *= n - i;
      a %= mod;
      b *= i + 1;
      b %= mod;
    }
    ans = (a * powmod(b, mod - 2, mod)) % mod;
  }

  return ans;
}

int main() {
  ll N, K;
  cin >> N >> K;
  K = min(ll(42), K);
  vector<ll> A(N, 0);

  rep(i, 0, N) { cin >> A[i]; }

  rep(j, 0, K) {
    vector<ll> light(N);
    rep(i, 0, N) {
      ll l = max(ll(0), i - A[i]);
      ll r = min(N - 1, i + A[i]);

      light[l]++;
      if (r + 1 < N)
        light[r + 1]--;
    }

    rep(i, 1, N) light[i] += light[i - 1];
    A = light;
  }

  rep(i, 0, N) {
    cout << A[i];
    if (i < N - 1)
      cout << " ";
  }

  cout << endl;

  // cout << setprecision(8) << ans << endl;  // For double
}


Error: TLE

Fixed submission:

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

using ll = long long int;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rrep(i, a, b) for (int i = a; i >= b; i--)
#define fore(i, a) for (auto &i : a)
#define all(x) (x).begin(), (x).end()

#define pi 3.14159265358979323846

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;
}

ll cnt_rep = 0;
ll powmod(ll N, ll P, ll M) {
  cnt_rep++;
  if (P == 0)
    return 1;
  if (P % 2 == 0) {
    ll t = powmod(N, P / 2, M);
    return t * t % M;
  }
  return (N * powmod(N, P - 1, M)) % M;
}

ll gcd(ll a, ll b) {
  ll resi, g, l;
  if (a > b) {
    g = a;
    l = b;
  } else if (b > a) {
    g = b;
    l = a;
  } else {
    return a;
  }
  resi = g % l;
  if (resi != 0) {
    return gcd(l, resi);
  } else {
    return l;
  }
}

template <typename T> void remove(std::vector<T> &vector, unsigned int index) {
  vector.erase(vector.begin() + index);
}

int ans = 0;
int N, M, Q;

template <typename T> void showall(vector<T> v) {
  rep(i, 0, v.size()) { cout << v[i] << " "; }
  cout << endl;
}

template <typename T> ll com(T n, T m, T mod) {
  ll a = 1, b = 1, ans;
  if (n == m || m == 0) {
    ans = 1;
  } else {
    for (ll i = 0; i < m; i++) {
      a *= n - i;
      a %= mod;
      b *= i + 1;
      b %= mod;
    }
    ans = (a * powmod(b, mod - 2, mod)) % mod;
  }

  return ans;
}

int main() {
  ll N, K;
  cin >> N >> K;
  vector<ll> A(N);

  rep(i, 0, N) { cin >> A[i]; }

  rep(j, 0, K) {
    vector<ll> light(N);
    rep(i, 0, N) {
      ll L = A[i];
      for (ll k = i - L; k <= i + L; k++) {
        if (k < 0 || k > N - 1)
          continue;
        light[k]++;
      }
    }
    A = light;
  }

  rep(i, 0, N) {
    cout << A[i];
    if (i < N - 1)
      cout << " ";
  }

  cout << endl;

  // cout << setprecision(8) << ans << endl;  // For double
}