Problem p02721 (C++) — buggy submission, verdict: Runtime Error

// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>

using namespace std;

//----------------------- Print Function ----------------------//

inline void print() { cout << endl; }
template <typename First, typename... Rest>
void print(const First &first, const Rest &...rest) {
  cout << first << ' ';
  print(rest...);
}

template <typename T> void print(const vector<T> &v) {
  for (auto e : v)
    cout << e << ' ';
  cout << endl;
}

//------------------------- Libraries -------------------------//

template <int MOD> struct Fp {
  long long val;
  constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr Fp operator+(const Fp &r) const noexcept { return Fp(*this) += r; }
  constexpr Fp operator-(const Fp &r) const noexcept { return Fp(*this) -= r; }
  constexpr Fp operator*(const Fp &r) const noexcept { return Fp(*this) *= r; }
  constexpr Fp operator/(const Fp &r) const noexcept { return Fp(*this) /= r; }
  constexpr Fp &operator+=(const Fp &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr Fp &operator-=(const Fp &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr Fp &operator*=(const Fp &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr Fp &operator/=(const Fp &r) noexcept {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      long long t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const Fp &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const Fp &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};
using mint = Fp<1000000007>;

//--------------------------- Solve ---------------------------//

void solve() {
  int N, K, C;
  cin >> N >> K >> C;
  string s;
  cin >> s;
  s = '#' + s;
  vector<int> left(K + 1), right(K + 1);

  int cnt = 1;
  for (int i = 1; i <= N & cnt <= K; i++) {
    if (s[i] == 'o') {
      left[cnt] = i;
      cnt++;
      i += C;
    }
  }
  cnt = K;
  for (int i = N; i >= 0 && cnt >= 0; i--) {
    if (s[i] == 'o') {
      right[cnt] = i;
      cnt--;
      i -= C;
    }
  }

  vector<int> ans;
  for (int i = 1; i <= K; i++) {
    if (left[i] == right[i])
      ans.push_back(left[i]);
  }

  print(ans);
}

int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  solve();

  return 0;
}

Error: WA

Fixed submission:

// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>

using namespace std;

//----------------------- Print Function ----------------------//

inline void print() { cout << endl; }
template <typename First, typename... Rest>
void print(const First &first, const Rest &...rest) {
  cout << first << ' ';
  print(rest...);
}

template <typename T> void print(const vector<T> &v) {
  for (auto e : v)
    cout << e << ' ';
  cout << endl;
}

//------------------------- Libraries -------------------------//

template <int MOD> struct Fp {
  long long val;
  constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr Fp operator+(const Fp &r) const noexcept { return Fp(*this) += r; }
  constexpr Fp operator-(const Fp &r) const noexcept { return Fp(*this) -= r; }
  constexpr Fp operator*(const Fp &r) const noexcept { return Fp(*this) *= r; }
  constexpr Fp operator/(const Fp &r) const noexcept { return Fp(*this) /= r; }
  constexpr Fp &operator+=(const Fp &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr Fp &operator-=(const Fp &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr Fp &operator*=(const Fp &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr Fp &operator/=(const Fp &r) noexcept {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      long long t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const Fp &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const Fp &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};
using mint = Fp<1000000007>;

//--------------------------- Solve ---------------------------//

void solve() {
  int N, K, C;
  cin >> N >> K >> C;
  string s;
  cin >> s;
  s = '#' + s;
  vector<int> left(K + 1), right(K + 1);

  int cnt = 1;
  for (int i = 1; i <= N; i++) {
    if (s[i] == 'o') {
      left[cnt] = i;
      cnt++;
      i += C;
    }
  }
  cnt = K;
  for (int i = N; i >= 0 && cnt >= 0; i--) {
    if (s[i] == 'o') {
      right[cnt] = i;
      cnt--;
      i -= C;
    }
  }

  vector<int> ans;
  for (int i = 1; i <= K; i++) {
    if (left[i] == right[i])
      ans.push_back(left[i]);
  }

  print(ans);
}

int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  solve();

  return 0;
}