Problem p03074 (C++)

Buggy submission (status: Runtime Error):
/*Function Template*/
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int MAX = 510000;
const int MOD = 1000000007;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define ALL(a) (a).begin(), (a).end()
#define IOS                                                                    \
  ios::sync_with_stdio(0);                                                     \
  cin.tie(0);                                                                  \
  cout.tie(0);
ll fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (ll i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
ll Len(ll n) {
  ll s = 0;
  while (n != 0)
    s++, n /= 10;
  return s;
}

ll Sint(ll n) {
  ll m = 0, s = 0, a = n;
  while (a != 0)
    s++, a /= 10;
  for (ll i = s - 1; i >= 0; i--)
    m += n / ((ll)pow(10, i)) - (n / ((ll)pow(10, i + 1))) * 10;
  return m;
}

ll Svec(vector<ll> v) {
  ll n = 0;
  for (ll i = 0; i < v.size(); i++)
    n += v[i];
  return n;
}

ll GCD(ll a, ll b) {
  ll r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return b;
}

ll LCM(ll a, ll b) {
  ll c = a, d = b, r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return c / b * d;
}

ll Factorial(ll n) {
  ll m = 1;
  while (n >= 1)
    m *= n, n--;
  return m;
}

vector<pair<char, ll>> runlength(string s, vector<pair<char, ll>> p) {
  ll x = 1;
  if (s.size() == 1) {
    p.push_back(pair<char, ll>(s[0], 1));
    return p;
  }
  for (ll i = 0; i < s.size() - 1; i++) {
    if (s[i] == s[i + 1]) {
      x++;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[i], x));
      }
    } else {
      p.push_back(pair<char, ll>(s[i], x));
      x = 1;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[s.size() - 1], x));
      }
    }
  }
  return p;
}

ll COM(ll n, ll k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

const int MAX_N = 100010;
vector<bool> sieve_of_eratosthenes() {
  vector<bool> isPrime(MAX_N + 1, true);
  for (int i = 2; i <= MAX_N; i++) {
    if (isPrime[i]) {
      for (int j = 2 * i; j <= MAX_N; j += i) {
        isPrime[j] = false;
      }
    }
  }
  return isPrime;
}

/*↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓*/
int main() {
  IOS;
  ll n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  vector<ll> nums;
  if (s[0] == '0')
    nums.push_back(0);
  for (ll i = 0; i < s.size();) {
    ll j = i;
    while (j < s.size() && s[i] == s[j])
      j++;
    nums.push_back(j - i);
    i = j;
  }
  if (s.back() == '0')
    nums.push_back(0);
  vector<ll> sums(nums.size(), 0);
  rep(i, nums.size()) sums[i + 1] = sums[i] + nums[i];
  ll res = 0;
  for (ll left = 0; left < sums.size(); left += 2) {
    ll right = left + k * 2 + 1;
    if (right >= sums.size())
      right = (ll)sums.size() - 1;
    res = max(res, sums[right] - sums[left]);
  }
  cout << res << endl;
}


Fixed submission:
/*Function Template*/
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int MAX = 510000;
const int MOD = 1000000007;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define ALL(a) (a).begin(), (a).end()
#define IOS                                                                    \
  ios::sync_with_stdio(0);                                                     \
  cin.tie(0);                                                                  \
  cout.tie(0);
ll fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (ll i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
ll Len(ll n) {
  ll s = 0;
  while (n != 0)
    s++, n /= 10;
  return s;
}

ll Sint(ll n) {
  ll m = 0, s = 0, a = n;
  while (a != 0)
    s++, a /= 10;
  for (ll i = s - 1; i >= 0; i--)
    m += n / ((ll)pow(10, i)) - (n / ((ll)pow(10, i + 1))) * 10;
  return m;
}

ll Svec(vector<ll> v) {
  ll n = 0;
  for (ll i = 0; i < v.size(); i++)
    n += v[i];
  return n;
}

ll GCD(ll a, ll b) {
  ll r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return b;
}

ll LCM(ll a, ll b) {
  ll c = a, d = b, r, tmp;
  /*自然数 a > b を確認・入替*/
  if (a < b) {
    tmp = a, a = b, b = tmp;
  }
  /*ユークリッドの互除法*/
  r = a % b;
  while (r != 0) {
    a = b, b = r, r = a % b;
  }
  return c / b * d;
}

ll Factorial(ll n) {
  ll m = 1;
  while (n >= 1)
    m *= n, n--;
  return m;
}

vector<pair<char, ll>> runlength(string s, vector<pair<char, ll>> p) {
  ll x = 1;
  if (s.size() == 1) {
    p.push_back(pair<char, ll>(s[0], 1));
    return p;
  }
  for (ll i = 0; i < s.size() - 1; i++) {
    if (s[i] == s[i + 1]) {
      x++;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[i], x));
      }
    } else {
      p.push_back(pair<char, ll>(s[i], x));
      x = 1;
      if (i == s.size() - 2) {
        p.push_back(pair<char, ll>(s[s.size() - 1], x));
      }
    }
  }
  return p;
}

ll COM(ll n, ll k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

const int MAX_N = 100010;
vector<bool> sieve_of_eratosthenes() {
  vector<bool> isPrime(MAX_N + 1, true);
  for (int i = 2; i <= MAX_N; i++) {
    if (isPrime[i]) {
      for (int j = 2 * i; j <= MAX_N; j += i) {
        isPrime[j] = false;
      }
    }
  }
  return isPrime;
}

/*↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓*/
int main() {
  IOS;
  ll n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  vector<ll> nums;
  if (s[0] == '0')
    nums.push_back(0);
  for (ll i = 0; i < s.size();) {
    ll j = i;
    while (j < s.size() && s[i] == s[j])
      j++;
    nums.push_back(j - i);
    i = j;
  }
  if (s.back() == '0')
    nums.push_back(0);
  vector<ll> sums(nums.size() + 1, 0);
  rep(i, nums.size()) sums[i + 1] = sums[i] + nums[i];
  ll res = 0;
  for (ll left = 0; left < sums.size(); left += 2) {
    ll right = left + k * 2 + 1;
    if (right >= sums.size())
      right = (ll)sums.size() - 1;
    res = max(res, sums[right] - sums[left]);
  }
  cout << res << endl;
}