Problem p03043 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

using namespace std;

typedef unsigned uint;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ldbl;
typedef pair<int, int> pii;
typedef pair<uint, uint> puu;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<double, double> pdd;
typedef vector<int> vi;
typedef vector<uint> vu;
typedef vector<ll> vll;
typedef vector<ull> vull;
typedef vector<pii> vpii;
typedef vector<puu> vpuu;
typedef vector<pll> vpll;
typedef vector<pull> vpull;
typedef vector<string> vstr;
typedef vector<double> vdbl;
typedef vector<ldbl> vldbl;
#define pb push_back
#define ppb pop_back
#define pfr push_front
#define ppfr pop_front
#define emp emplace
#define empb emplace_back
#define be begin
#define rbe rbegin
#define all(x) (x).be(), (x).end()
#define rall(x) (x).rbe(), (x).rend()
#define fir first
#define sec second
#define mkp make_pair
#define brif(cond)                                                             \
  if (cond)                                                                    \
  break
#define ctif(cond)                                                             \
  if (cond)                                                                    \
  continue
#define retif(cond)                                                            \
  if (cond)                                                                    \
  return
void canhazfast() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
}
template <typename T> T gcd(T a, T b) { return b ? gcd(b, a % b) : a; }
template <typename T> T extgcd(T a, T b, T &x, T &y) {
  T x0 = 1, y0 = 0, x1 = 0, y1 = 1;
  while (b) {
    T q = a / b;
    a %= b;
    swap(a, b);
    x0 -= q * x1;
    swap(x0, x1);
    y0 -= q * y1;
    swap(y0, y1);
  }
  x = x0;
  y = y0;
  return a;
}
int ctz(uint x) { return __builtin_ctz(x); }
int ctzll(ull x) { return __builtin_ctzll(x); }
int clz(uint x) { return __builtin_clz(x); }
int clzll(ull x) { return __builtin_clzll(x); }
int popcnt(uint x) { return __builtin_popcount(x); }
int popcntll(ull x) { return __builtin_popcountll(x); }
int bsr(uint x) { return 31 ^ clz(x); }
int bsrll(ull x) { return 63 ^ clzll(x); }

#define MX 100016

double dp[MX];

int main() {
  // canhazfast();

  int n, k;
  double ans = 0.0;

  scanf("%d%d", &n, &k);
  for (int i = k; i <= max(2 * k, n); ++i)
    dp[i] = 1.0;
  for (int i = k - 1; i > 0; --i)
    dp[i] = 0.5 * dp[2 * i];
  for (int i = 1; i <= n; ++i)
    ans += dp[i];
  ans /= n;
  printf("%.10lf\n", ans);

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

using namespace std;

typedef unsigned uint;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ldbl;
typedef pair<int, int> pii;
typedef pair<uint, uint> puu;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<double, double> pdd;
typedef vector<int> vi;
typedef vector<uint> vu;
typedef vector<ll> vll;
typedef vector<ull> vull;
typedef vector<pii> vpii;
typedef vector<puu> vpuu;
typedef vector<pll> vpll;
typedef vector<pull> vpull;
typedef vector<string> vstr;
typedef vector<double> vdbl;
typedef vector<ldbl> vldbl;
#define pb push_back
#define ppb pop_back
#define pfr push_front
#define ppfr pop_front
#define emp emplace
#define empb emplace_back
#define be begin
#define rbe rbegin
#define all(x) (x).be(), (x).end()
#define rall(x) (x).rbe(), (x).rend()
#define fir first
#define sec second
#define mkp make_pair
#define brif(cond)                                                             \
  if (cond)                                                                    \
  break
#define ctif(cond)                                                             \
  if (cond)                                                                    \
  continue
#define retif(cond)                                                            \
  if (cond)                                                                    \
  return
void canhazfast() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
}
template <typename T> T gcd(T a, T b) { return b ? gcd(b, a % b) : a; }
template <typename T> T extgcd(T a, T b, T &x, T &y) {
  T x0 = 1, y0 = 0, x1 = 0, y1 = 1;
  while (b) {
    T q = a / b;
    a %= b;
    swap(a, b);
    x0 -= q * x1;
    swap(x0, x1);
    y0 -= q * y1;
    swap(y0, y1);
  }
  x = x0;
  y = y0;
  return a;
}
int ctz(uint x) { return __builtin_ctz(x); }
int ctzll(ull x) { return __builtin_ctzll(x); }
int clz(uint x) { return __builtin_clz(x); }
int clzll(ull x) { return __builtin_clzll(x); }
int popcnt(uint x) { return __builtin_popcount(x); }
int popcntll(ull x) { return __builtin_popcountll(x); }
int bsr(uint x) { return 31 ^ clz(x); }
int bsrll(ull x) { return 63 ^ clzll(x); }

#define MX 100016

double dp[2 * MX];

int main() {
  // canhazfast();

  int n, k;
  double ans = 0.0;

  scanf("%d%d", &n, &k);
  for (int i = k; i <= max(2 * k, n); ++i)
    dp[i] = 1.0;
  for (int i = k - 1; i > 0; --i)
    dp[i] = 0.5 * dp[2 * i];
  for (int i = 1; i <= n; ++i)
    ans += dp[i];
  ans /= n;
  printf("%.10lf\n", ans);

  return 0;
}