Problem p03074 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repo(i, n) for (int i = 1; i < (int)(n); i++)
#define pb push_back
#define mp make_pair
#define np next_permutation
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define mod 1000000007
#define pi acos(-1.0)
const ll INF = 1LL << 61;
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }
ll jou(ll N, ll P) {
  if (P == 0)
    return 1;
  if (P % 2 == 0) {
    ll t = jou(N, P / 2);
    return t * t % mod;
  }
  return (N * jou(N, P - 1)) % mod;
} // jou(n,mod-2)で逆元
// intの最大値2147483647 ≒ 2×10^9
// long longの最大値9223372036854775807 ≒ 9×10^18
//'大文字'+=32;    で小文字に
//   cout << fixed << setprecision (20);   小数点以下2０桁まで
// 実行時間制約2秒では２×10^8回くらいまで計算できる

int main() {
  int n, k;
  string s;
  cin >> n >> k >> s;

  bool stz = false;
  bool goz = false;
  vector<int> p = {};
  rep(i, n) {
    if (i == 0 && s[i] == '0')
      stz = true;
    if (i == 0 && s[i] == '1')
      p.pb(i);
    if (i - 1 >= 0 && s[i - 1] == '0' && s[i] == '1')
      p.pb(i);
    if (i + 1 < n && s[i] == '1' && s[i + 1] == '0')
      p.pb(i);
    if (i == n - 1 && s[i] == '1')
      p.pb(i);
    if (i == n - 1 && s[i] == '0')
      goz = true;
  }

  int m = p.size();
  if (m == 0) {
    cout << n << endl;
    return 0;
  }
  int zr = m / 2 - 1;
  if (stz)
    zr++;
  if (goz)
    zr++;

  if (zr <= k) {
    cout << n << endl;
    return 0;
  }

  int ans = 0;
  if (stz)
    ans = max(ans, p[2 * k - 1] + 1);
  if (goz)
    ans = max(ans, n - 1 - p[m - 2 * k] + 1);
  rep(i, m) {
    if (2 * i + 2 * k + 1 >= n)
      break;
    ans = max(ans, p[2 * i + 2 * k + 1] - p[2 * i] + 1);
  }

  cout << ans << endl;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repo(i, n) for (int i = 1; i < (int)(n); i++)
#define pb push_back
#define mp make_pair
#define np next_permutation
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define mod 1000000007
#define pi acos(-1.0)
const ll INF = 1LL << 61;
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }
ll jou(ll N, ll P) {
  if (P == 0)
    return 1;
  if (P % 2 == 0) {
    ll t = jou(N, P / 2);
    return t * t % mod;
  }
  return (N * jou(N, P - 1)) % mod;
} // jou(n,mod-2)で逆元
// intの最大値2147483647 ≒ 2×10^9
// long longの最大値9223372036854775807 ≒ 9×10^18
//'大文字'+=32;    で小文字に
//   cout << fixed << setprecision (20);   小数点以下2０桁まで
// 実行時間制約2秒では２×10^8回くらいまで計算できる

int main() {
  int n, k;
  string s;
  cin >> n >> k >> s;

  bool stz = false;
  bool goz = false;
  vector<int> p = {};
  rep(i, n) {
    if (i == 0 && s[i] == '0')
      stz = true;
    if (i == 0 && s[i] == '1')
      p.pb(i);
    if (i - 1 >= 0 && s[i - 1] == '0' && s[i] == '1')
      p.pb(i);
    if (i + 1 < n && s[i] == '1' && s[i + 1] == '0')
      p.pb(i);
    if (i == n - 1 && s[i] == '1')
      p.pb(i);
    if (i == n - 1 && s[i] == '0')
      goz = true;
  }

  int m = p.size();
  if (m == 0) {
    cout << n << endl;
    return 0;
  }
  int zr = m / 2 - 1;
  if (stz)
    zr++;
  if (goz)
    zr++;

  if (zr <= k) {
    cout << n << endl;
    return 0;
  }

  int ans = 0;
  if (stz)
    ans = max(ans, p[2 * k - 1] + 1);
  if (goz)
    ans = max(ans, n - 1 - p[m - 2 * k] + 1);
  rep(i, m) {
    if (2 * i + 2 * k + 1 >= m)
      break;
    ans = max(ans, p[2 * i + 2 * k + 1] - p[2 * i] + 1);
  }

  cout << ans << endl;
}