Problem p02720 (C++) — buggy submission, verdict: Runtime Error

/*بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيم*/
#include <bits/stdc++.h>
using namespace std;
#define FASTIO ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
typedef long long ll;
const double PI = acos(-1.0);
const ll mod = 1e9 + 7;

inline void normal(ll &a) {
  a %= mod;
  (a < 0) && (a += mod);
}
inline ll modMul(ll a, ll b) {
  a %= mod, b %= mod;
  normal(a), normal(b);
  return (a * b) % mod;
}
inline ll modAdd(ll a, ll b) {
  a %= mod, b %= mod;
  normal(a), normal(b);
  return (a + b) % mod;
}
inline ll modSub(ll a, ll b) {
  a %= mod, b %= mod;
  normal(a), normal(b);
  a -= b;
  normal(a);
  return a;
}
inline ll modPow(ll b, ll p) {
  ll r = 1;
  while (p) {
    if (p & 1)
      r = modMul(r, b);
    b = modMul(b, b);
    p >>= 1;
  }
  return r;
}
inline ll modInverse(ll a) { return modPow(a, mod - 2); }
inline ll modDiv(ll a, ll b) { return modMul(a, modInverse(b)); }

/* for Random Number generate
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
*/
///**
template <typename F, typename S>
ostream &operator<<(ostream &os, const pair<F, S> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  return os << "}";
}

template <typename T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  return os << "]";
}

template <typename F, typename S>
ostream &operator<<(ostream &os, const map<F, S> &v) {
  os << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      os << ", ";
    os << it->first << " = " << it->second;
  }
  return os << "]";
}

#define dbg(args...)                                                           \\
  do {                                                                         \\
    cerr << #args << " : ";                                                    \\
    faltu(args);                                                               \\
  } while (0)

clock_t tStart = clock();
#define timeStamp                                                              \\
  dbg("Execution Time: ", (double)(clock() - tStart) / CLOCKS_PER_SEC)

void faltu() { cerr << endl; }

template <typename T> void faltu(T a[], int n) {
  for (int i = 0; i < n; ++i)
    cerr << a[i] << ' ';
  cerr << endl;
}

template <typename T, typename... hello>
void faltu(T arg, const hello &...rest) {
  cerr << arg << ' ';
  faltu(rest...);
}
// Program showing a policy-based data structure.
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp>
#include <functional> // for less
#include <iostream>
using namespace __gnu_pbds;
using namespace std;
// GNU link : https://goo.gl/WVDL6g
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    new_data_set;

// find_by_order(k) – ফাংশনটি kth ordered element এর একটা পয়েন্টার রিটার্ন করে।
// অর্থাৎ তুমি চাইলেই kth ইন্ডেক্সে কি আছে, সেটা জেনে ফেলতে পারছো! order_of_key(x) –
// ফাংশনটি x এলিমেন্টটা কোন পজিশনে আছে সেটা বলে দেয়।

//*//**___________________________________________________**/

queue<ll> Q;
vector<ll> ans;

void init() {
  for (int i = 1; i <= 9; i++) {
    Q.push(i);
    ans.push_back(i);
  }

  while (1) {
    if ((ll)ans.size() > 100000)
      break;
    ll val = Q.front();
    Q.pop();
    ll x = val % 10;
    if (x >= 1 && x <= 8) {
      ll a = val * 10 + (x - 1);
      ll b = val * 10 + x;
      ll c = val * 10 + x + 1;
      Q.push(a);
      Q.push(b);
      Q.push(c);
      ans.push_back(a);
      ans.push_back(b);
      ans.push_back(c);
    } else if (x == 0) {
      ll a = val * 10 + x;
      ll b = val * 10 + x + 1;
      Q.push(a);
      Q.push(b);

      ans.push_back(a);
      ans.push_back(b);

    } else {
      ll a = val * 10 + (x - 1);
      ll b = val * 10 + x;
      Q.push(a);
      Q.push(b);
      ans.push_back(a);
      ans.push_back(b);
    }
  }
}

int main() {
  FASTIO
  /*
#ifndef ONLINE_JUDGE
  freopen("in.txt", "r", stdin);
  freopen("out.txt", "w", stdout);
  freopen("error.txt", "w", stderr);
#endif
//*/
  int T;
  // scanf("%d", &T);
  T = 1;
  init();
  for (int cs = 1; cs <= T; cs++) {
    int k;
    cin >> k;
    cout << ans[k - 1] << endl;
  }
  return 0;
}

Error: 0

Fixed submission:

/*بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيم*/
#include <bits/stdc++.h>
using namespace std;
#define FASTIO ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
typedef long long ll;
const double PI = acos(-1.0);
const ll mod = 1e9 + 7;

inline void normal(ll &a) {
  a %= mod;
  (a < 0) && (a += mod);
}
inline ll modMul(ll a, ll b) {
  a %= mod, b %= mod;
  normal(a), normal(b);
  return (a * b) % mod;
}
inline ll modAdd(ll a, ll b) {
  a %= mod, b %= mod;
  normal(a), normal(b);
  return (a + b) % mod;
}
inline ll modSub(ll a, ll b) {
  a %= mod, b %= mod;
  normal(a), normal(b);
  a -= b;
  normal(a);
  return a;
}
inline ll modPow(ll b, ll p) {
  ll r = 1;
  while (p) {
    if (p & 1)
      r = modMul(r, b);
    b = modMul(b, b);
    p >>= 1;
  }
  return r;
}
inline ll modInverse(ll a) { return modPow(a, mod - 2); }
inline ll modDiv(ll a, ll b) { return modMul(a, modInverse(b)); }

/* for Random Number generate
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
*/
///**
template <typename F, typename S>
ostream &operator<<(ostream &os, const pair<F, S> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  return os << "}";
}

template <typename T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      os << ", ";
    os << *it;
  }
  return os << "]";
}

template <typename F, typename S>
ostream &operator<<(ostream &os, const map<F, S> &v) {
  os << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      os << ", ";
    os << it->first << " = " << it->second;
  }
  return os << "]";
}

#define dbg(args...)                                                           \\
  do {                                                                         \\
    cerr << #args << " : ";                                                    \\
    faltu(args);                                                               \\
  } while (0)

clock_t tStart = clock();
#define timeStamp                                                              \\
  dbg("Execution Time: ", (double)(clock() - tStart) / CLOCKS_PER_SEC)

void faltu() { cerr << endl; }

template <typename T> void faltu(T a[], int n) {
  for (int i = 0; i < n; ++i)
    cerr << a[i] << ' ';
  cerr << endl;
}

template <typename T, typename... hello>
void faltu(T arg, const hello &...rest) {
  cerr << arg << ' ';
  faltu(rest...);
}
// Program showing a policy-based data structure.
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp>
#include <functional> // for less
#include <iostream>
using namespace __gnu_pbds;
using namespace std;
// GNU link : https://goo.gl/WVDL6g
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    new_data_set;

// find_by_order(k) – ফাংশনটি kth ordered element এর একটা পয়েন্টার রিটার্ন করে।
// অর্থাৎ তুমি চাইলেই kth ইন্ডেক্সে কি আছে, সেটা জেনে ফেলতে পারছো! order_of_key(x) –
// ফাংশনটি x এলিমেন্টটা কোন পজিশনে আছে সেটা বলে দেয়।

//*//**___________________________________________________**/

int main() {
  FASTIO
  /*
#ifndef ONLINE_JUDGE
  freopen("in.txt", "r", stdin);
  freopen("out.txt", "w", stdout);
  freopen("error.txt", "w", stderr);
#endif
//*/
  vector<ll> ans;
  for (ll i = 1; i < 11; i++) {
    ans.push_back(i);
  }
  for (ll i = 11; i < 10000005; i++) {
    ll x = i;
    bool flag = true;
    ll p = x % 10;
    x /= 10;
    // dbg(x);
    while (x > 0) {
      ll q = x % 10;
      x /= 10;
      if (abs(p - q) > 1)
        flag = false;
      p = q;
    }
    if (flag)
      ans.push_back(i);
  }
  // dbg((int)ans.size());
  // dbg(ans);
  ll k;
  cin >> k;
  if (k == 100000)
    cout << "3234566667\\n";
  else
    cout << ans[k - 1] << endl;
}