Problem p02647 (C++) — buggy submission, verdict: Runtime Error

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

// #define int long long
#define rep(i, n) for (long long i = (long long)(0); i < (long long)(n); ++i)
#define reps(i, n) for (long long i = (long long)(1); i <= (long long)(n); ++i)
#define rrep(i, n) for (long long i = ((long long)(n)-1); i >= 0; i--)
#define rreps(i, n) for (long long i = ((long long)(n)); i > 0; i--)
#define irep(i, m, n)                                                          \\
  for (long long i = (long long)(m); i < (long long)(n); ++i)
#define ireps(i, m, n)                                                         \\
  for (long long i = (long long)(m); i <= (long long)(n); ++i)
#define SORT(v, n) sort(v, v + n);
#define REVERSE(v, n) reverse(v, v + n);
#define vsort(v) sort(v.begin(), v.end());
#define all(v) v.begin(), v.end()
#define mp(n, m) make_pair(n, m);
#define cout(d) cout << d << endl;
#define coutd(d) cout << std::setprecision(10) << d << endl;
#define cinline(n) getline(cin, n);
#define replace_all(s, b, a) replace(s.begin(), s.end(), b, a);
#define PI (acos(-1))
#define FILL(v, n, x) fill(v, v + n, x);
#define sz(x) long long(x.size())

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vs = vector<string>;
using vpll = vector<pair<ll, ll>>;
using vtp = vector<tuple<ll, ll, ll>>;
using vb = vector<bool>;

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

const ll INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, k;
  cin >> n >> k;
  vll a(n);
  rep(i, n) cin >> a[i];

  rep(_, k) {
    // imos
    vll l(n + 1);
    rep(i, n) {
      l[i]++;
      ll r = min(n, i + a[i] + 1);
      l[r]--;
    }
    rep(i, n) l[i + 1] += l[i];

    vll r(n + 1);
    rrep(i, n) {
      r[i + 1]++;
      ll l = max(0LL, i + 1 - a[i] - 1);
      r[l]--;
    }
    rrep(i, n) r[i] += r[i + 1];

    // rep(i,n+1) cout<<l[i]<<' ';
    // cout<<endl;
    // rep(i,n+1) cout<<r[i]<<" ";
    // cout<<endl;

    rep(i, n) { a[i] = l[i] + r[i + 1] - 1; }

    bool flg = true;
    rep(i, n) {
      if (a[i] != n)
        flg = false;
    }
    if (flg) {
      rep(i, n) cout << a[i] << endl;
      return 0;
    }
  }

  rep(i, n) cout << a[i] << endl;
}

Error: WA

Fixed submission:

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

// #define int long long
#define rep(i, n) for (long long i = (long long)(0); i < (long long)(n); ++i)
#define reps(i, n) for (long long i = (long long)(1); i <= (long long)(n); ++i)
#define rrep(i, n) for (long long i = ((long long)(n)-1); i >= 0; i--)
#define rreps(i, n) for (long long i = ((long long)(n)); i > 0; i--)
#define irep(i, m, n)                                                          \\
  for (long long i = (long long)(m); i < (long long)(n); ++i)
#define ireps(i, m, n)                                                         \\
  for (long long i = (long long)(m); i <= (long long)(n); ++i)
#define SORT(v, n) sort(v, v + n);
#define REVERSE(v, n) reverse(v, v + n);
#define vsort(v) sort(v.begin(), v.end());
#define all(v) v.begin(), v.end()
#define mp(n, m) make_pair(n, m);
#define cout(d) cout << d << endl;
#define coutd(d) cout << std::setprecision(10) << d << endl;
#define cinline(n) getline(cin, n);
#define replace_all(s, b, a) replace(s.begin(), s.end(), b, a);
#define PI (acos(-1))
#define FILL(v, n, x) fill(v, v + n, x);
#define sz(x) long long(x.size())

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vs = vector<string>;
using vpll = vector<pair<ll, ll>>;
using vtp = vector<tuple<ll, ll, ll>>;
using vb = vector<bool>;

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

const ll INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, k;
  cin >> n >> k;
  vll a(n);
  rep(i, n) cin >> a[i];

  rep(_, k) {
    // imos
    vll l(n + 1);
    rep(i, n) {
      l[i]++;
      ll r = min(n + 1, i + a[i] + 1);
      l[r]--;
    }
    rep(i, n) l[i + 1] += l[i];

    vll r(n + 1);
    rrep(i, n) {
      r[i + 1]++;
      ll l = max(0LL, i + 1 - a[i] - 1);
      r[l]--;
    }
    rrep(i, n) r[i] += r[i + 1];

    // rep(i,n+1) cout<<l[i]<<' ';
    // cout<<endl;
    // rep(i,n+1) cout<<r[i]<<" ";
    // cout<<endl;

    rep(i, n) { a[i] = l[i] + r[i + 1] - 1; }

    bool flg = true;
    rep(i, n) {
      if (a[i] != n)
        flg = false;
    }
    if (flg) {
      rep(i, n) cout << a[i] << endl;
      return 0;
    }
  }

  rep(i, n) cout << a[i] << endl;
}