Problem p01295 (C++) — buggy submission, verdict: Runtime Error

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

#define fi first
#define se second
#define repl(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define repr(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define rep(i, n) repl(i, 0, n)
#define each(itr, v) for (auto itr : v)
#define pb(s) push_back(s)
#define all(x) (x).begin(), (x).end()
#define dbg(x) cout << #x " = " << x << endl
#define print(x) cout << x << endl
#define maxch(x, y) x = max(x, y)
#define minch(x, y) x = min(x, y)
#define uni(x) x.erase(unique(all(x)), x.end())
#define exist(x, y) (find(all(x), y) != x.end())
#define bcnt(x) bitset<32>(x).count()

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef pair<P, int> PPI;
typedef pair<int, P> PIP;
typedef pair<ll, ll> PL;
typedef pair<P, ll> PPL;
typedef set<int> S;

#define INF INT_MAX / 3
#define MAX_N 1000000001

int main() {
  // cin.sync_with_stdio(false);
  int n, k;
  while (cin >> n >> k, n) {
    ll d = 0, i = 1;

    while (true) {
      if (d < n && n <= d + i * pow(10, i - 1) * 9) {
        int num =
            (n - d) / i + (((n - d) % i) ? 1 : 0) + (int)pow(10, i - 1) - 1;
        int p = i * (num - (int)pow(10, i - 1) + 1) - (n - d) + 1;
        if (k >= p) {
          cout << to_string(num).substr(i - p);
          num++;
          k -= p;
          while (to_string(num).size() <= k) {
            k -= to_string(num).size();
            cout << to_string(num);
            num++;
          }
          if (k)
            cout << to_string(num).substr(0, k);
        } else {
          cout << to_string(num).substr(i - p, k);
        }
        cout << endl;
        break;
      } else {
        d += i * pow(10, i - 1) * 9;
        i++;
      }
    }
  }

  return 0;
}

Error: 0

Fixed submission:

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

#define fi first
#define se second
#define repl(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define repr(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define rep(i, n) repl(i, 0, n)
#define each(itr, v) for (auto itr : v)
#define pb(s) push_back(s)
#define all(x) (x).begin(), (x).end()
#define dbg(x) cout << #x " = " << x << endl
#define print(x) cout << x << endl
#define maxch(x, y) x = max(x, y)
#define minch(x, y) x = min(x, y)
#define uni(x) x.erase(unique(all(x)), x.end())
#define exist(x, y) (find(all(x), y) != x.end())
#define bcnt(x) bitset<32>(x).count()

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef pair<P, int> PPI;
typedef pair<int, P> PIP;
typedef pair<ll, ll> PL;
typedef pair<P, ll> PPL;
typedef set<int> S;

#define INF INT_MAX / 3
#define MAX_N 1000000001

int main() {
  // cin.sync_with_stdio(false);
  int n, k;
  while (cin >> n >> k, n) {
    // n++;
    ll d = 0, i = 1;

    while (true) {
      if (d < n && n < d + i * pow(10, i - 1) * 9) {
        int num =
            (n - d) / i + (((n - d) % i) ? 1 : 0) + (int)pow(10, i - 1) - 1;
        int p = i * (num - (int)pow(10, i - 1) + 1) - (n - d) + 1;
        // cout << num << " " << p << endl;
        if (k >= p) {
          cout << to_string(num).substr(i - p, p);
          num++;
          k -= p;
          while (to_string(num).size() <= k) {
            k -= to_string(num).size();
            cout << to_string(num);
            num++;
          }
          // cout << k << endl;
          if (k)
            cout << to_string(num).substr(0, k);
          // if (k) printf("%d", num / (int)pow(10, to_string(num).size() - k));
        } else {
          // num = num % (int)pow(10, p);
          // printf("%d", num / (int)pow(10, to_string(num).size() - k));
          cout << to_string(num).substr(i - p, k);
        }
        printf("\\n");
        break;
      } else {
        d += i * pow(10, i - 1) * 9;
        i++;
      }
    }
  }

  return 0;
}