Problem p01503 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
#include <type_traits>
using namespace std;

using ll = int64_t;
// #define int ll

#define FOR(i, a, b) for (int i = int(a); i < int(b); i++)
#define REP(i, b) FOR(i, 0, b)
#define MP make_pair
#define PB push_back
#define EB emplace_back
#define ALL(x) x.begin(), x.end()
auto &errStream = cerr;
#ifdef LOCAL
#define cerr (cerr << "-- line " << __LINE__ << " -- ")
#else
class CerrDummy {
} cerrDummy;
template <class T> CerrDummy &operator<<(CerrDummy &cd, const T &) {
  return cd;
}
using charTDummy = char;
using traitsDummy = char_traits<charTDummy>;
CerrDummy &operator<<(CerrDummy &cd,
                      basic_ostream<charTDummy, traitsDummy> &(
                          basic_ostream<charTDummy, traitsDummy> &)) {
  return cd;
}
#define cerr cerrDummy
#endif
#define REACH cerr << "reached" << endl
#define DMP(x) cerr << #x << ":" << x << endl
#define ZERO(x) memset(x, 0, sizeof(x))
#define ONE(x) memset(x, -1, sizeof(x))

using pi = pair<int, int>;
using vi = vector<int>;
using ld = long double;

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

template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  REP(i, (int)v.size()) {
    if (i)
      os << ",";
    os << v[i];
  }
  os << "}";
  return os;
}

ll read() {
  ll i;
  scanf("%" SCNd64, &i);
  return i;
}

void printSpace() { printf(" "); }

void printEoln() { printf("\\n"); }

void print(ll x, int suc = 1) {
  printf("%" PRId64, x);
  if (suc == 1)
    printEoln();
  if (suc == 2)
    printSpace();
}

string readString() {
  static char buf[3341000];
  scanf("%s", buf);
  return string(buf);
}

char *readCharArray() {
  static char buf[3341000];
  static int bufUsed = 0;
  char *ret = buf + bufUsed;
  scanf("%s", ret);
  bufUsed += strlen(ret) + 1;
  return ret;
}

template <class T, class U> void chmax(T &a, U b) {
  if (a < b)
    a = b;
}

template <class T, class U> void chmin(T &a, U b) {
  if (b < a)
    a = b;
}

template <class T> T Sq(const T &t) { return t * t; }

#define CAPITAL
void Yes(bool ex = true) {
#ifdef CAPITAL
  cout << "YES" << endl;
#else
  cout << "Yes" << endl;
#endif
  if (ex)
    exit(0);
}
void No(bool ex = true) {
#ifdef CAPITAL
  cout << "NO" << endl;
#else
  cout << "No" << endl;
#endif
  if (ex)
    exit(0);
}

const ll infLL = LLONG_MAX / 3;

#ifdef int
const int inf = infLL;
#else
const int inf = INT_MAX / 2 - 100;
#endif

int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }

int lcm(int a, int b) { return a / gcd(a, b) * b; }

int extgcd(int a, int b, int &x, int &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  } else {
    int g = extgcd(b, a % b, y, x);
    y -= a / b * x;
    return g;
  }
}

signed main() {
  int w = read(), d = read(), n = read(), m = read(), t = read();
  int g, x, y;
  g = extgcd(m, t, x, y);
  int f = t / g;
  if (x < 0)
    x += f;
  assert(x >= 0);
  int e = gcd(t, w + d);
  int cur = 0;
  int cnt = 0;
  int remG = 0, remE = 0;
  int last = -1;
  REP(i, t) {
    if (remG == 0) {
      if (cur < n)
        last = i;
      cur += x;
      if (cur >= f)
        cur -= f;
      remG = g - 1;
    } else {
      remG--;
    }
    if (remE == 0) {
      cnt += (last < i - w);
      remE = e - 1;
    } else {
      remE--;
    }
  }
  cout << fixed << setprecision(20) << double(cnt) / (t / e) << endl;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#include <type_traits>
using namespace std;

using ll = int64_t;
// #define int ll

#define FOR(i, a, b) for (int i = int(a); i < int(b); i++)
#define REP(i, b) FOR(i, 0, b)
#define MP make_pair
#define PB push_back
#define EB emplace_back
#define ALL(x) x.begin(), x.end()
auto &errStream = cerr;
#ifdef LOCAL
#define cerr (cerr << "-- line " << __LINE__ << " -- ")
#else
class CerrDummy {
} cerrDummy;
template <class T> CerrDummy &operator<<(CerrDummy &cd, const T &) {
  return cd;
}
using charTDummy = char;
using traitsDummy = char_traits<charTDummy>;
CerrDummy &operator<<(CerrDummy &cd,
                      basic_ostream<charTDummy, traitsDummy> &(
                          basic_ostream<charTDummy, traitsDummy> &)) {
  return cd;
}
#define cerr cerrDummy
#endif
#define REACH cerr << "reached" << endl
#define DMP(x) cerr << #x << ":" << x << endl
#define ZERO(x) memset(x, 0, sizeof(x))
#define ONE(x) memset(x, -1, sizeof(x))

using pi = pair<int, int>;
using vi = vector<int>;
using ld = long double;

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

template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  REP(i, (int)v.size()) {
    if (i)
      os << ",";
    os << v[i];
  }
  os << "}";
  return os;
}

ll read() {
  ll i;
  scanf("%" SCNd64, &i);
  return i;
}

void printSpace() { printf(" "); }

void printEoln() { printf("\\n"); }

void print(ll x, int suc = 1) {
  printf("%" PRId64, x);
  if (suc == 1)
    printEoln();
  if (suc == 2)
    printSpace();
}

string readString() {
  static char buf[3341000];
  scanf("%s", buf);
  return string(buf);
}

char *readCharArray() {
  static char buf[3341000];
  static int bufUsed = 0;
  char *ret = buf + bufUsed;
  scanf("%s", ret);
  bufUsed += strlen(ret) + 1;
  return ret;
}

template <class T, class U> void chmax(T &a, U b) {
  if (a < b)
    a = b;
}

template <class T, class U> void chmin(T &a, U b) {
  if (b < a)
    a = b;
}

template <class T> T Sq(const T &t) { return t * t; }

#define CAPITAL
void Yes(bool ex = true) {
#ifdef CAPITAL
  cout << "YES" << endl;
#else
  cout << "Yes" << endl;
#endif
  if (ex)
    exit(0);
}
void No(bool ex = true) {
#ifdef CAPITAL
  cout << "NO" << endl;
#else
  cout << "No" << endl;
#endif
  if (ex)
    exit(0);
}

const ll infLL = LLONG_MAX / 3;

#ifdef int
const int inf = infLL;
#else
const int inf = INT_MAX / 2 - 100;
#endif

int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }

const int V = 1000000010;
bitset<V> buf;

signed main() {
  int w = read(), d = read(), n = read(), m = read(), t = read();
  int e = gcd(t, w + d);
  int cur = 0;
  m %= t;
  REP(i, n) {
    buf[cur] = 1;
    cur += m;
    if (cur >= t)
      cur -= t;
  }
  int cnt = 0;
  int rem = 0;
  int last = -1;
  REP(i, t) {
    if (buf[i])
      last = i;
    if (rem == 0) {
      if (last < i - w)
        cnt++;
      rem = e - 1;
    } else {
      rem--;
    }
  }
  cout << fixed << setprecision(20) << double(cnt) / (t / e) << endl;
}