Problem p00254 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <cassert>

#include <ccomplex>
#include <cctype>
#include <cerrno>
#include <cfenv>
#include <cfloat>
#include <cinttypes>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstdbool>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctgmath>
#include <ctime>
#include <cwchar>
#include <cwctype>

// C++
#include <algorithm>
#include <array>
#include <atomic>
#include <bitset>
#include <chrono>
#include <complex>
#include <condition_variable>
#include <deque>
#include <exception>
#include <forward_list>
#include <fstream>
#include <functional>
#include <future>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <mutex>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <valarray>
#include <vector>
// #include <boost/foreach.hpp>
// #include <boost/range/algorithm.hpp>
#define rep(i, j, k) for (int i = (int)j; i < (int)k; i++)
#define ll long long
#define Sort(v) sort(all(v))
#define INF 1e9
#define LINF 1e18
#define END return 0
#define pb push_back
#define se second
#define fi first
#define pb push_back
#define all(v) (v).begin(), (v).end()
#define MP make_pair
#define MOD 1000000007LL
#define int long long
using namespace std;
int day[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};
struct edge {
  int to, cost;
};
// typedef pair<int,int> P;

bool isupper(char c) {
  if ('A' <= c && c <= 'Z')
    return 1;
  return 0;
}
bool islower(char c) {
  if ('a' <= c && c <= 'z')
    return 1;
  return 0;
}
bool isPrime(int x) {
  if (x == 1)
    return 0;
  if (x == 2)
    return 1;
  if (x % 2 == 0)
    return 0;
  for (int i = 3; i * i <= x; i++)
    if (x % i == 0)
      return 0;
  return 1;
}
bool iskaibun(string s) {
  for (int i = 0; i < s.size() / 2; i++)
    if (s[i] != s[s.size() - i - 1])
      return 0;
  return 1;
}
bool isnumber(char c) { return ('0' <= c && c <= '9'); }
bool isalpha(char c) { return (isupper(c) && islower(c)); }
void printvi(vector<int> v) {
  rep(i, 0, v.size()) {
    if (i)
      cout << " ";
    cout << v[i];
  }
  cout << endl;
}
void printvil(vector<int> v) {
  rep(i, 0, v.size()) { cout << v[i] << endl; }
}
void printvvi(vector<vector<int>> v) {
  rep(i, 0, v.size()) {
    rep(j, 0, v[i].size()) {
      if (j)
        cout << " ";
      cout << v[i][j];
    }
    cout << endl;
  }
}
void printvstr(vector<string> v) {
  rep(i, 0, v.size()) { cout << v[i] << endl; }
}

signed main() {
  string s;
  while (1) {
    cin >> s;
    if (s == "0000")
      break;
    auto cmp = [&](char a, char b) { return a > b; };
    if (s[0] == s[1] and s[1] == s[2] and s[2] == s[3]) {
      cout << "NA" << endl;
      continue;
    }
    int i = 0;
    for (; s != "6174"; i++) {
      sort(all(s));
      int a1 = stol(s);
      sort(all(s), cmp);
      int a2 = stol(s);
      int a3 = a2 - a1;
      s = to_string(a3);
    }
    cout << i << endl;
  }
}
/*
 */


Fixed submission:
#include <cassert>

#include <ccomplex>
#include <cctype>
#include <cerrno>
#include <cfenv>
#include <cfloat>
#include <cinttypes>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstdbool>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctgmath>
#include <ctime>
#include <cwchar>
#include <cwctype>

// C++
#include <algorithm>
#include <array>
#include <atomic>
#include <bitset>
#include <chrono>
#include <complex>
#include <condition_variable>
#include <deque>
#include <exception>
#include <forward_list>
#include <fstream>
#include <functional>
#include <future>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <mutex>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <valarray>
#include <vector>
// #include <boost/foreach.hpp>
// #include <boost/range/algorithm.hpp>
#define rep(i, j, k) for (int i = (int)j; i < (int)k; i++)
#define ll long long
#define Sort(v) sort(all(v))
#define INF 1e9
#define LINF 1e18
#define END return 0
#define pb push_back
#define se second
#define fi first
#define pb push_back
#define all(v) (v).begin(), (v).end()
#define MP make_pair
#define MOD 1000000007LL
#define int long long
using namespace std;
int day[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};
struct edge {
  int to, cost;
};
// typedef pair<int,int> P;

bool isupper(char c) {
  if ('A' <= c && c <= 'Z')
    return 1;
  return 0;
}
bool islower(char c) {
  if ('a' <= c && c <= 'z')
    return 1;
  return 0;
}
bool isPrime(int x) {
  if (x == 1)
    return 0;
  if (x == 2)
    return 1;
  if (x % 2 == 0)
    return 0;
  for (int i = 3; i * i <= x; i++)
    if (x % i == 0)
      return 0;
  return 1;
}
bool iskaibun(string s) {
  for (int i = 0; i < s.size() / 2; i++)
    if (s[i] != s[s.size() - i - 1])
      return 0;
  return 1;
}
bool isnumber(char c) { return ('0' <= c && c <= '9'); }
bool isalpha(char c) { return (isupper(c) && islower(c)); }
void printvi(vector<int> v) {
  rep(i, 0, v.size()) {
    if (i)
      cout << " ";
    cout << v[i];
  }
  cout << endl;
}
void printvil(vector<int> v) {
  rep(i, 0, v.size()) { cout << v[i] << endl; }
}
void printvvi(vector<vector<int>> v) {
  rep(i, 0, v.size()) {
    rep(j, 0, v[i].size()) {
      if (j)
        cout << " ";
      cout << v[i][j];
    }
    cout << endl;
  }
}
void printvstr(vector<string> v) {
  rep(i, 0, v.size()) { cout << v[i] << endl; }
}

signed main() {
  string s;
  while (1) {
    cin >> s;
    if (s == "0000")
      break;
    auto cmp = [&](char a, char b) { return a > b; };
    if (s[0] == s[1] and s[1] == s[2] and s[2] == s[3]) {
      cout << "NA" << endl;
      continue;
    }
    int i = 0;
    for (; s != "6174"; i++) {
      sort(all(s));
      int a1 = stol(s);
      sort(all(s), cmp);
      int a2 = stol(s);
      int a3 = a2 - a1;
      s = to_string(a3);
      while (s.size() < 4) {
        s = "0" + s;
      }
      // cout<<s<<endl;
    }
    cout << i << endl;
  }
}
/*
 */