Problem p04048 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <bitset>
#include <cctype>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

#define int long long
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(a) (a).begin(), (a).end()
#define PB push_back
#define MP make_pair
#define FST first
#define SND second
#define SZ(a) (signed)((a).size())
#define EACH(i, c)                                                             \
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

using namespace std;

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;

const int MOD = 1000000007;
const char ENDL = '\n';

#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;

int solve(int a, int b) {
  if (b > a) {
    swap(a, b);
  }
  if (b == 0) {
    return 0;
  } else if (b == 1) {
    return a;
  } else {
    return b + solve(a - b, b);
  }
}

signed main(void) {
  ios::sync_with_stdio(false);
  cout.setf(ios::fixed, ios::floatfield);
  cout.precision(10);
  cin.tie(0);

  int n, x;
  cin >> n >> x;
  if (x > n / 2) {
    x = n - x;
  }

  cout << 3 * solve(n - x, x) << ENDL;

  return 0;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cctype>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

#define int long long
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(a) (a).begin(), (a).end()
#define PB push_back
#define MP make_pair
#define FST first
#define SND second
#define SZ(a) (signed)((a).size())
#define EACH(i, c)                                                             \
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

using namespace std;

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;

const int MOD = 1000000007;
const char ENDL = '\n';

#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;

int solve(int a, int b) {
  if (b > a) {
    swap(a, b);
  }
  if (b == 0) {
    return 0;
  } else if (b == 1) {
    return a;
  } else {
    return b * (a / b) + solve(a % b, b);
  }
}

signed main(void) {
  ios::sync_with_stdio(false);
  cout.setf(ios::fixed, ios::floatfield);
  cout.precision(10);
  cin.tie(0);

  int n, x;
  cin >> n >> x;
  if (x > n / 2) {
    x = n - x;
  }

  cout << 3 * solve(n - x, x) << ENDL;

  return 0;
}