Problem p03683 (C++)

Buggy submission (status: Time Limit Exceeded):
#define TEST_MODE false

#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#include "bits/stdc++.h"
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i, a, b) for (int i = (a); i < (b); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
#define rrep2(i, a, b) for (int i = (a)-1; i >= b; --i)
#define range(i, a, b, c) for (int i = a; c > 0 ? i < b : i > b; i += c)
#define chmax(a, b) (a = (a) < (b) ? (b) : (a))
#define chmin(a, b) (a = (a) > (b) ? (b) : (a))
using ll = long long;
using ull = unsigned long long;
using ld = long double;
#define all(a) begin(a), end(a)
#define ifnot(a) if (not(a))
#define int long long

#ifdef LOCAL_ENV

#if TEST_MODE == true
const bool test = true;
#define dump(x) cerr << #x << " = " << (x) << endl
#else
const bool test = false;
#define dump(x)
#endif

#else
const bool test = false;
#define dump(x)
#endif

int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};
const int INF = (int)1 << 60;
const ll INFL = (ll)1 << 60;
ll mod_n = (int)1e9 + 7;
const double eps = 1e-10;
typedef long double Real;
// return -1, 0, 1
int sgn(const Real &r) { return (r > eps) - (r < -eps); }
int sgn(const Real &a, const Real &b) { return sgn(a - b); }

//.....................
const int MAX = (int)2e5 + 5;

vector<string> split(const string &str, char sep) {
  vector<string> v;
  stringstream ss(str);
  string buffer;
  while (getline(ss, buffer, sep)) {
    v.push_back(buffer);
  }
  return v;
}

template <class InputIterator> int sum(InputIterator begin, InputIterator end) {
  return accumulate(begin, end, 0ll);
}

void solve();

signed main() {
  cout << fixed << setprecision(20);
  while (true) {
    solve();
  }
  return 0;
}

// class Mycin {
// 	bool flag = true;
// public:
// 	Mycin& operator >> (int& a) {flag = scanf("%lld", &a) != EOF; return
// *this;} 	Mycin& operator >> (char& a) {flag = scanf("%c", &a) != EOF; return
// *this;} 	Mycin& operator >> (string& s) {flag = (bool)(cin >> s); return
// *this;} 	operator bool() {return flag;} } mycin;

// class Mycout {
// public:
// 	Mycout& operator << (const int& a) {printf("%lld", a); return *this;}
// 	Mycout& operator << (const char c) {printf("%c", c); return *this;}
// 	Mycout& operator << (const string& s) {printf("%s", s.c_str()); return
// *this;} } mycout;

// #define cin mycin
// #define cout mycout
// #define endl '\n'

int N, M;

int ans() {
  if (N < M)
    swap(N, M);
  if (N - M > 1)
    return 0;
  if (N == M) {
    int res = 1;
    rep(loop, 2) {
      rep(i, N) {
        res *= i + 1;
        res %= mod_n;
      }
    }
    res *= 2;
    res %= mod_n;
    return res;
  }
  if (N - M == 1) {
    int res = 1;
    rep(loop, 2) {
      int A = (loop == 0 ? N : M);
      rep(i, A) {
        res *= i + 1;
        res %= mod_n;
      }
    }
    return res;
  }
}

void solve() {
  cin >> N >> M;
  cout << ans() << endl;
}


Fixed submission:
#define TEST_MODE false

#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#include "bits/stdc++.h"
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i, a, b) for (int i = (a); i < (b); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
#define rrep2(i, a, b) for (int i = (a)-1; i >= b; --i)
#define range(i, a, b, c) for (int i = a; c > 0 ? i < b : i > b; i += c)
#define chmax(a, b) (a = (a) < (b) ? (b) : (a))
#define chmin(a, b) (a = (a) > (b) ? (b) : (a))
using ll = long long;
using ull = unsigned long long;
using ld = long double;
#define all(a) begin(a), end(a)
#define ifnot(a) if (not(a))
#define int long long

#ifdef LOCAL_ENV

#if TEST_MODE == true
const bool test = true;
#define dump(x) cerr << #x << " = " << (x) << endl
#else
const bool test = false;
#define dump(x)
#endif

#else
const bool test = false;
#define dump(x)
#endif

int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};
const int INF = (int)1 << 60;
const ll INFL = (ll)1 << 60;
ll mod_n = (int)1e9 + 7;
const double eps = 1e-10;
typedef long double Real;
// return -1, 0, 1
int sgn(const Real &r) { return (r > eps) - (r < -eps); }
int sgn(const Real &a, const Real &b) { return sgn(a - b); }

//.....................
const int MAX = (int)2e5 + 5;

vector<string> split(const string &str, char sep) {
  vector<string> v;
  stringstream ss(str);
  string buffer;
  while (getline(ss, buffer, sep)) {
    v.push_back(buffer);
  }
  return v;
}

template <class InputIterator> int sum(InputIterator begin, InputIterator end) {
  return accumulate(begin, end, 0ll);
}

void solve();

signed main() {
  cout << fixed << setprecision(20);
  solve();
  // while (true) {
  //     solve();
  // }
  return 0;
}

// class Mycin {
// 	bool flag = true;
// public:
// 	Mycin& operator >> (int& a) {flag = scanf("%lld", &a) != EOF; return
// *this;} 	Mycin& operator >> (char& a) {flag = scanf("%c", &a) != EOF; return
// *this;} 	Mycin& operator >> (string& s) {flag = (bool)(cin >> s); return
// *this;} 	operator bool() {return flag;} } mycin;

// class Mycout {
// public:
// 	Mycout& operator << (const int& a) {printf("%lld", a); return *this;}
// 	Mycout& operator << (const char c) {printf("%c", c); return *this;}
// 	Mycout& operator << (const string& s) {printf("%s", s.c_str()); return
// *this;} } mycout;

// #define cin mycin
// #define cout mycout
// #define endl '\n'

int N, M;

int ans() {
  if (N < M)
    swap(N, M);
  if (N - M > 1)
    return 0;
  if (N == M) {
    int res = 1;
    rep(loop, 2) {
      rep(i, N) {
        res *= i + 1;
        res %= mod_n;
      }
    }
    res *= 2;
    res %= mod_n;
    return res;
  }
  if (N - M == 1) {
    int res = 1;
    rep(loop, 2) {
      int A = (loop == 0 ? N : M);
      rep(i, A) {
        res *= i + 1;
        res %= mod_n;
      }
    }
    return res;
  }
}

void solve() {
  cin >> N >> M;
  cout << ans() << endl;
}