Problem p00254 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define foreach(it, c)                                                         \\
  for (__typeof__((c).begin()) it = (c).begin(); it != (c).end(); ++it)
#define rforeach(it, c)                                                        \\
  for (__typeof__((c).rbegin()) it = (c).rbegin(); it != (c).rend(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define CL(arr, val) memset(arr, val, sizeof(arr))
#define COPY(dest, src) memcpy(dest, src, sizeof(dest))
#define ten(n) ((long long)(1e##n))
#define bin(n) (1LL << (n))
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define revrep(i, n) for (int i = (n); i >= 0; --i)
#define pb push_back

template <class T> void chmax(T &a, const T &b) { a = max(a, b); }
template <class T> void chmin(T &a, const T &b) { a = min(a, b); }

template <class T> T round_up(T a, T b) { return (a + b - 1) / b; }

template <class T> void uniq(vector<T> &c) {
  sort(c.begin(), c.end());
  c.erase(unique(c.begin(), c.end()), c.end());
}

template <class T> string to_s(const T &a) {
  ostringstream os;
  os << a;
  return os.str();
}
template <class T> T to_T(const string &s) {
  istringstream is(s);
  T res;
  is >> res;
  return res;
}

template <class T, class U> ostream &operator<<(ostream &os, pair<T, U> &p) {
  os << "( " << p.first << ", " << p.second << " )";
  return os;
}

template <class T>
void print(T a, int n, const string &deli = " ", int br = 1) {
  for (int i = 0; i < n; ++i) {
    cout << a[i];
    if (i + 1 != n)
      cout << deli;
  }
  while (br--)
    cout << endl;
}
template <class T>
void print(const T &c, const string &deli = " ", int br = 1) {
  foreach (it, c) {
    cout << *it;
    if (++it != c.end())
      cout << deli;
    --it;
  }
  while (br--)
    cout << endl;
}
template <class T> void print2d(T a, int w, int h, int width = -1, int br = 1) {
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (width != -1)
        cout.width(width);
      cout << a[i][j] << ' ';
    }
    cout << endl;
  }
  while (br--)
    cout << endl;
}

template <class T> void input(T &a, int n) {
  for (int i = 0; i < n; ++i)
    cin >> a[i];
}
template <class T> void input(T *a, int n) {
  for (int i = 0; i < n; ++i)
    cin >> a[i];
}

void fix_pre(int n) {
  cout.setf(ios::fixed, ios::floatfield);
  cout.precision(10);
}
void fast_io() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}
#define trace(x) (cout << #x << ": " << (x) << endl)

bool in_rect(int x, int y, int w, int h) {
  return 0 <= x && x < w && 0 <= y && y < h;
}

typedef long long ll;
typedef pair<int, int> pint;

// y(v): v>^<  y(^): ^>v<
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

const double PI = acos(-1.0);

#define F first
#define S second

const int inf = ten(6);
int dp[11111];
int recur(int n) {
  if (dp[n] != -1)
    return dp[n];

  string n_str = to_s(n);
  n_str += string(4 - n_str.size(), '0');

  sort(all(n_str));
  int s = to_T<int>(n_str);
  reverse(all(n_str));
  int l = to_T<int>(n_str);

  return dp[n] = l - s == n ? inf : recur(l - s) + 1;
}
int main() {
  CL(dp, -1);
  dp[0] = inf;
  dp[6174] = 0;

  int n;
  while (cin >> n, n) {
    int r = recur(n);
    if (r < inf)
      cout << r << endl;
    else
      cout << "NA" << endl;
  }
}

Error: 0

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define foreach(it, c)                                                         \\
  for (__typeof__((c).begin()) it = (c).begin(); it != (c).end(); ++it)
#define rforeach(it, c)                                                        \\
  for (__typeof__((c).rbegin()) it = (c).rbegin(); it != (c).rend(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define CL(arr, val) memset(arr, val, sizeof(arr))
#define COPY(dest, src) memcpy(dest, src, sizeof(dest))
#define ten(n) ((long long)(1e##n))
#define bin(n) (1LL << (n))
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define revrep(i, n) for (int i = (n); i >= 0; --i)
#define pb push_back

template <class T> void chmax(T &a, const T &b) { a = max(a, b); }
template <class T> void chmin(T &a, const T &b) { a = min(a, b); }

template <class T> T round_up(T a, T b) { return (a + b - 1) / b; }

template <class T> void uniq(vector<T> &c) {
  sort(c.begin(), c.end());
  c.erase(unique(c.begin(), c.end()), c.end());
}

template <class T> string to_s(const T &a) {
  ostringstream os;
  os << a;
  return os.str();
}
template <class T> T to_T(const string &s) {
  istringstream is(s);
  T res;
  is >> res;
  return res;
}

template <class T, class U> ostream &operator<<(ostream &os, pair<T, U> &p) {
  os << "( " << p.first << ", " << p.second << " )";
  return os;
}

template <class T>
void print(T a, int n, const string &deli = " ", int br = 1) {
  for (int i = 0; i < n; ++i) {
    cout << a[i];
    if (i + 1 != n)
      cout << deli;
  }
  while (br--)
    cout << endl;
}
template <class T>
void print(const T &c, const string &deli = " ", int br = 1) {
  foreach (it, c) {
    cout << *it;
    if (++it != c.end())
      cout << deli;
    --it;
  }
  while (br--)
    cout << endl;
}
template <class T> void print2d(T a, int w, int h, int width = -1, int br = 1) {
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (width != -1)
        cout.width(width);
      cout << a[i][j] << ' ';
    }
    cout << endl;
  }
  while (br--)
    cout << endl;
}

template <class T> void input(T &a, int n) {
  for (int i = 0; i < n; ++i)
    cin >> a[i];
}
template <class T> void input(T *a, int n) {
  for (int i = 0; i < n; ++i)
    cin >> a[i];
}

void fix_pre(int n) {
  cout.setf(ios::fixed, ios::floatfield);
  cout.precision(10);
}
void fast_io() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}
#define trace(x) (cout << #x << ": " << (x) << endl)

bool in_rect(int x, int y, int w, int h) {
  return 0 <= x && x < w && 0 <= y && y < h;
}

typedef long long ll;
typedef pair<int, int> pint;

// y(v): v>^<  y(^): ^>v<
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

const double PI = acos(-1.0);

#define F first
#define S second

const int inf = ten(6);
int dp[11111];
int recur(int n) {
  if (dp[n] != -1)
    return dp[n];

  string n_str = to_s(n);
  sort(all(n_str));
  int s = to_T<int>(n_str);
  reverse(all(n_str));
  int l = to_T<int>(n_str);

  return dp[n] = recur(l - s) + 1;
}
int main() {
  CL(dp, -1);
  dp[0] = inf;
  dp[6174] = 0;

  int n;
  while (cin >> n, n) {
    int r = recur(n);
    if (r < inf)
      cout << r << endl;
    else
      cout << "NA" << endl;
  }
}