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

#include <iostream>
#include <string>

using namespace std;

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

  int a[200000];
  int b[200000];
  for (int i = 0, idx = 0; i < n; ++i)
    if (s[i] == 'o') {
      a[idx++] = i;
      i += c;
    }
  for (int i = n - 1, idx = k - 1; i >= 0; --i)
    if (s[i] == 'o') {
      b[idx--] = i;
      i -= c;
    }

  for (int i = 0; i < k; ++i)
    if (a[i] == b[i])
      cout << a[i] + 1 << endl;
  return 0;
}


Error: 0

Fixed submission:

#include <algorithm>
#include <boost/multiprecision/cpp_int.hpp>
#include <cstdio>
#include <deque>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace boost::multiprecision;
using namespace std;
#define BEGIN                                                                  \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(NULL);                                                               \\
  cout.tie(NULL)
#define END return EXIT_SUCCESS
#define up(I, A, B) for (auto I = (A); I <= (B); ++I)
#define dw(I, A, B) for (auto I = (A); I >= (B); --I)
#define rep(I, N) up(I, 0, N - 1)
#define all(C) (C).begin(), (C).end()
#define rall(C) (C).rbegin(), (C).rend()
#define ft first
#define sd second
#define mp make_pair
#define mt make_tuple
#define pf push_front
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define rs resize
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
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;
}
template <class T> inline void in(T &p) { cin >> p; }
template <class T1, class T2> inline void in(T1 &p1, T2 &p2) {
  cin >> p1 >> p2;
}
template <class T1, class T2, class T3> inline void in(T1 &p1, T2 &p2, T3 &p3) {
  cin >> p1 >> p2 >> p3;
}
template <class T1, class T2, class T3, class T4>
inline void in(T1 &p1, T2 &p2, T3 &p3, T4 &p4) {
  cin >> p1 >> p2 >> p3 >> p4;
}
template <class T1, class T2, class T3, class T4, class T5>
inline void in(T1 &p1, T2 &p2, T3 &p3, T4 &p4, T5 &p5) {
  cin >> p1 >> p2 >> p3 >> p4 >> p5;
}
template <class T> inline void ins(T &p) {
  for_each(all(p), in<decltype(p[0])>);
}
template <class T> inline void out(T p) { cout << p << endl; }
template <class T1, class T2> inline void out(T1 p1, T2 p2) {
  cout << p1 << " " << p2 << endl;
}
template <class T1, class T2, class T3> inline void out(T1 p1, T2 p2, T3 p3) {
  cout << p1 << " " << p2 << " " << p3 << endl;
}
template <class T1, class T2, class T3, class T4>
inline void out(T1 p1, T2 p2, T3 p3, T4 p4) {
  cout << p1 << " " << p2 << " " << p3 << " " << p4 << endl;
}
inline void out(ld p) { printf("%.12Lf\\n", p); }
template <class T> inline void outml(T p) {
  for_each(all(p), out<decltype(p[0])>);
}
template <class T> inline void outol(T V) {
  int n = V.size();
  rep(i, n) cout << V[i] << " \\n"[i == n - 1];
}
inline void solve(void) {
  long N, K, C;
  string S;
  in(N, K, C, S);
  vector<long> L(K), R(K);
  for (long i = 0, pos = 0; i < N; ++i)
    if (S[i] == 'o') {
      L[pos++] = i;
      i += C;
    }
  for (long i = N - 1, pos = K - 1; i >= 0; --i)
    if (S[i] == 'o') {
      R[pos--] = i;
      i -= C;
    }
  rep(i, K) if (L[i] == R[i]) out(L[i] + 1);
}
int main(int argc, char **argv) {
  BEGIN;
  solve();
  END;
}