Problem p02780 (C++)

Buggy submission (status: Runtime Error):

#include <bits/stdc++.h>

class kin {
public:
  inline void open(FILE *, int);
  inline void close(void);
  inline void scan(void);
  inline kin &operator>(char &);
  inline kin &operator>(int &);
  inline kin &operator>(long long &);
  inline kin &operator>(double &);
  inline kin &operator>(long double &);
  inline kin &operator>(char *);
  template <class T> inline void get(T *, int);

private:
  FILE *fp;
  char *buf;
  int siz;
  int idx;
} in;

class kout {
public:
  inline void open(FILE *, int);
  inline void close(void);
  inline void print(void);
  inline kout &operator<(char);
  inline kout &operator<(int);
  inline kout &operator<(long long);
  inline kout &operator<(double);
  inline kout &operator<(long double);
  inline kout &operator<(const char *);
  template <class T> inline void put(T *, int, char, char);

private:
  FILE *fp;
  char *buf;
  int siz;
  int idx;
} out;

inline void chmax(long long val, long long &var) {
  if (val > var)
    var = val;
}

int main(int argc, char **argv) {
  in.open(stdin, 512);
  out.open(stdout, 512);
  in.scan();
  int n, k;
  in > n > k;
  long long d[100001];
  d[0] = 0LL;
  for (int i = 1; i <= n; ++i) {
    long long p;
    in > p;
    d[i] = d[i - 1] + p + 1LL;
  }
  long long ans = d[k];
  for (int i = k + 1; i <= n; ++i)
    chmax(d[i] - d[i - k], ans);
  out < (long double)ans / 2.0L < '\n';
  out.print();
  in.close();
  out.close();
  return 0;
}

inline void kin::open(FILE *fparg, int sizarg) {
  fp = fparg;
  buf = new char[sizarg];
  siz = sizarg;
  idx = 0;
  return;
}
inline void kin::close(void) {
  fp = nullptr;
  delete[] buf;
  buf = nullptr;
  siz = 0;
  idx = 0;
  return;
}
inline void kin::scan(void) {
  int readsiz =
      (int)std::fread((void *)buf, (std::size_t)1, (std::size_t)siz, fp);
  if (readsiz != siz)
    buf[readsiz] = '\x00';
  idx = 0;
  return;
}
inline kin &kin::operator>(char &var) {
  if (!buf[idx]) {
    var = '\x00';
    return *this;
  }
  var = buf[idx];
  if (++idx == siz)
    scan();
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(int &var) {
  if (!buf[idx]) {
    var = 0;
    return *this;
  }
  int sign = -1;
  if (buf[idx] == '-') {
    sign = 1;
    if (++idx == siz)
      scan();
  }
  var = 0;
  while (buf[idx] >= '0') {
    var = var * 10 - (int)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(long long &var) {
  if (!buf[idx]) {
    var = 0LL;
    return *this;
  }
  long long sign = -1LL;
  if (buf[idx] == '-') {
    sign = 1LL;
    if (++idx == siz)
      scan();
  };
  var = 0LL;
  while (buf[idx] >= '0') {
    var = var * 10LL - (long long)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(double &var) {
  if (!buf[idx]) {
    var = 0.0;
    return *this;
  }
  double sign = -1.0;
  if (buf[idx] == '-') {
    sign = 1.0;
    if (++idx == siz)
      scan();
  }
  var = 0.0;
  while (buf[idx] >= '0') {
    var = var * 10.0 - (double)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  if (buf[idx] == '.') {
    if (++idx == siz)
      scan();
    double dig = 1.0;
    while (buf[idx] >= '0') {
      var -= (double)(buf[idx] - '0') * (dig /= 10.0);
      if (++idx == siz)
        scan();
    }
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(long double &var) {
  if (!buf[idx]) {
    var = 0.0L;
    return *this;
  }
  long double sign = -1.0L;
  if (buf[idx] == '-') {
    sign = 1.0L;
    if (++idx == siz)
      scan();
  }
  var = 0.0L;
  while (buf[idx] >= '0') {
    var = var * 10.0L - (long double)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  if (buf[idx] == '.') {
    if (++idx == siz)
      scan();
    long double dig = 1.0L;
    while (buf[idx] >= '0') {
      var -= (long double)(buf[idx] - '0') * (dig /= 10.0L);
      if (++idx == siz)
        scan();
    }
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(char *str) {
  if (!buf[idx]) {
    str[0] = '\x00';
    return *this;
  }
  int ptr = 0;
  while (buf[idx] >= '!') {
    str[ptr++] = buf[idx];
    if (++idx == siz)
      scan();
  }
  str[ptr] = '\x00';
  if (++idx == siz)
    scan();
  return *this;
}
template <class T> inline void kin::get(T *arr, int num) {
  for (int i = 0; i < num; ++i)
    (*this) > arr[i];
  return;
}

inline void kout::open(FILE *fparg, int sizarg) {
  fp = fparg;
  buf = new char[sizarg];
  siz = sizarg;
  idx = 0;
  return;
}
inline void kout::close(void) {
  fp = nullptr;
  delete[] buf;
  buf = nullptr;
  siz = 0;
  idx = 0;
  return;
}
inline void kout::print(void) {
  std::fwrite((void *)buf, (std::size_t)1, (std::size_t)idx, fp);
  idx = 0;
  return;
}
inline kout &kout::operator<(char val) {
  buf[idx] = val;
  if (++idx == siz)
    print();
  return *this;
}
inline kout &kout::operator<(int val) {
  if (val < 0) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1;
  char dig[10];
  int ptr = 0;
  do {
    int tmp = val / 10;
    dig[ptr++] = (char)-(val - tmp * 10) + '0';
    val = tmp;
  } while (val);
  while (ptr--) {
    buf[idx] = dig[ptr];
    if (++idx == siz)
      print();
  }
  return *this;
}
inline kout &kout::operator<(long long val) {
  if (val < 0LL) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1LL;
  char dig[19];
  int ptr = 0;
  do {
    long long tmp = val / 10LL;
    dig[ptr++] = (char)-(val - tmp * 10LL) + '0';
    val = tmp;
  } while (val);
  while (ptr--) {
    buf[idx] = dig[ptr];
    if (++idx == siz)
      print();
  }
  return *this;
}
inline kout &kout::operator<(double val) {
  if (val < 0.0) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1.0;
  double dig = 1.0;
  while (val / dig <= -10.0)
    dig *= 10.0;
  int tmp;
  while (dig >= 1.0) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (double)tmp * dig;
    dig /= 10.0;
  }
  buf[idx] = '.';
  if (++idx == siz)
    print();
  for (int i = 0; i < 12; ++i) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (double)tmp * dig;
    dig /= 10.0;
  }
  return *this;
}
inline kout &kout::operator<(long double val) {
  if (val < 0.0L) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1.0L;
  long double dig = 1.0L;
  while (val / dig <= -10.0L)
    dig *= 10.0L;
  int tmp;
  while (dig >= 1.0L) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (long double)tmp * dig;
    dig /= 10.0L;
  }
  buf[idx] = '.';
  if (++idx == siz)
    print();
  for (int i = 0; i < 16; ++i) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (long double)tmp * dig;
    dig /= 10.0L;
  }
  return *this;
}
inline kout &kout::operator<(const char *str) {
  for (int i = 0; str[i]; ++i) {
    buf[idx] = str[i];
    if (++idx == siz)
      print();
  }
  return *this;
}
template <class T> inline void kout::put(T *arr, int num, char dlm, char end) {
  --num;
  for (int i = 0; i < num; ++i)
    (*this) < arr[i] < dlm;
  (*this) < arr[num] < end;
  return;
}


Fixed submission:

#include <bits/stdc++.h>

class kin {
public:
  inline void open(FILE *, int);
  inline void close(void);
  inline void scan(void);
  inline kin &operator>(char &);
  inline kin &operator>(int &);
  inline kin &operator>(long long &);
  inline kin &operator>(double &);
  inline kin &operator>(long double &);
  inline kin &operator>(char *);
  template <class T> inline void get(T *, int);

private:
  FILE *fp;
  char *buf;
  int siz;
  int idx;
} in;

class kout {
public:
  inline void open(FILE *, int);
  inline void close(void);
  inline void print(void);
  inline kout &operator<(char);
  inline kout &operator<(int);
  inline kout &operator<(long long);
  inline kout &operator<(double);
  inline kout &operator<(long double);
  inline kout &operator<(const char *);
  template <class T> inline void put(T *, int, char, char);

private:
  FILE *fp;
  char *buf;
  int siz;
  int idx;
} out;

inline void chmax(long long val, long long &var) {
  if (val > var)
    var = val;
}

int main(int argc, char **argv) {
  in.open(stdin, 512);
  out.open(stdout, 512);
  in.scan();
  int n, k;
  in > n > k;
  long long d[200001];
  d[0] = 0LL;
  for (int i = 1; i <= n; ++i) {
    long long p;
    in > p;
    d[i] = d[i - 1] + p + 1LL;
  }
  long long ans = d[k];
  for (int i = k + 1; i <= n; ++i)
    chmax(d[i] - d[i - k], ans);
  out < (long double)ans / 2.0L < '\n';
  out.print();
  in.close();
  out.close();
  return 0;
}

inline void kin::open(FILE *fparg, int sizarg) {
  fp = fparg;
  buf = new char[sizarg];
  siz = sizarg;
  idx = 0;
  return;
}
inline void kin::close(void) {
  fp = nullptr;
  delete[] buf;
  buf = nullptr;
  siz = 0;
  idx = 0;
  return;
}
inline void kin::scan(void) {
  int readsiz =
      (int)std::fread((void *)buf, (std::size_t)1, (std::size_t)siz, fp);
  if (readsiz != siz)
    buf[readsiz] = '\x00';
  idx = 0;
  return;
}
inline kin &kin::operator>(char &var) {
  if (!buf[idx]) {
    var = '\x00';
    return *this;
  }
  var = buf[idx];
  if (++idx == siz)
    scan();
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(int &var) {
  if (!buf[idx]) {
    var = 0;
    return *this;
  }
  int sign = -1;
  if (buf[idx] == '-') {
    sign = 1;
    if (++idx == siz)
      scan();
  }
  var = 0;
  while (buf[idx] >= '0') {
    var = var * 10 - (int)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(long long &var) {
  if (!buf[idx]) {
    var = 0LL;
    return *this;
  }
  long long sign = -1LL;
  if (buf[idx] == '-') {
    sign = 1LL;
    if (++idx == siz)
      scan();
  };
  var = 0LL;
  while (buf[idx] >= '0') {
    var = var * 10LL - (long long)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(double &var) {
  if (!buf[idx]) {
    var = 0.0;
    return *this;
  }
  double sign = -1.0;
  if (buf[idx] == '-') {
    sign = 1.0;
    if (++idx == siz)
      scan();
  }
  var = 0.0;
  while (buf[idx] >= '0') {
    var = var * 10.0 - (double)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  if (buf[idx] == '.') {
    if (++idx == siz)
      scan();
    double dig = 1.0;
    while (buf[idx] >= '0') {
      var -= (double)(buf[idx] - '0') * (dig /= 10.0);
      if (++idx == siz)
        scan();
    }
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(long double &var) {
  if (!buf[idx]) {
    var = 0.0L;
    return *this;
  }
  long double sign = -1.0L;
  if (buf[idx] == '-') {
    sign = 1.0L;
    if (++idx == siz)
      scan();
  }
  var = 0.0L;
  while (buf[idx] >= '0') {
    var = var * 10.0L - (long double)(buf[idx] - '0');
    if (++idx == siz)
      scan();
  }
  if (buf[idx] == '.') {
    if (++idx == siz)
      scan();
    long double dig = 1.0L;
    while (buf[idx] >= '0') {
      var -= (long double)(buf[idx] - '0') * (dig /= 10.0L);
      if (++idx == siz)
        scan();
    }
  }
  var *= sign;
  if (++idx == siz)
    scan();
  return *this;
}
inline kin &kin::operator>(char *str) {
  if (!buf[idx]) {
    str[0] = '\x00';
    return *this;
  }
  int ptr = 0;
  while (buf[idx] >= '!') {
    str[ptr++] = buf[idx];
    if (++idx == siz)
      scan();
  }
  str[ptr] = '\x00';
  if (++idx == siz)
    scan();
  return *this;
}
template <class T> inline void kin::get(T *arr, int num) {
  for (int i = 0; i < num; ++i)
    (*this) > arr[i];
  return;
}

inline void kout::open(FILE *fparg, int sizarg) {
  fp = fparg;
  buf = new char[sizarg];
  siz = sizarg;
  idx = 0;
  return;
}
inline void kout::close(void) {
  fp = nullptr;
  delete[] buf;
  buf = nullptr;
  siz = 0;
  idx = 0;
  return;
}
inline void kout::print(void) {
  std::fwrite((void *)buf, (std::size_t)1, (std::size_t)idx, fp);
  idx = 0;
  return;
}
inline kout &kout::operator<(char val) {
  buf[idx] = val;
  if (++idx == siz)
    print();
  return *this;
}
inline kout &kout::operator<(int val) {
  if (val < 0) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1;
  char dig[10];
  int ptr = 0;
  do {
    int tmp = val / 10;
    dig[ptr++] = (char)-(val - tmp * 10) + '0';
    val = tmp;
  } while (val);
  while (ptr--) {
    buf[idx] = dig[ptr];
    if (++idx == siz)
      print();
  }
  return *this;
}
inline kout &kout::operator<(long long val) {
  if (val < 0LL) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1LL;
  char dig[19];
  int ptr = 0;
  do {
    long long tmp = val / 10LL;
    dig[ptr++] = (char)-(val - tmp * 10LL) + '0';
    val = tmp;
  } while (val);
  while (ptr--) {
    buf[idx] = dig[ptr];
    if (++idx == siz)
      print();
  }
  return *this;
}
inline kout &kout::operator<(double val) {
  if (val < 0.0) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1.0;
  double dig = 1.0;
  while (val / dig <= -10.0)
    dig *= 10.0;
  int tmp;
  while (dig >= 1.0) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (double)tmp * dig;
    dig /= 10.0;
  }
  buf[idx] = '.';
  if (++idx == siz)
    print();
  for (int i = 0; i < 12; ++i) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (double)tmp * dig;
    dig /= 10.0;
  }
  return *this;
}
inline kout &kout::operator<(long double val) {
  if (val < 0.0L) {
    buf[idx] = '-';
    if (++idx == siz)
      print();
  } else
    val *= -1.0L;
  long double dig = 1.0L;
  while (val / dig <= -10.0L)
    dig *= 10.0L;
  int tmp;
  while (dig >= 1.0L) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (long double)tmp * dig;
    dig /= 10.0L;
  }
  buf[idx] = '.';
  if (++idx == siz)
    print();
  for (int i = 0; i < 16; ++i) {
    buf[idx] = (char)-(tmp = (int)(val / dig)) + '0';
    if (++idx == siz)
      print();
    val -= (long double)tmp * dig;
    dig /= 10.0L;
  }
  return *this;
}
inline kout &kout::operator<(const char *str) {
  for (int i = 0; str[i]; ++i) {
    buf[idx] = str[i];
    if (++idx == siz)
      print();
  }
  return *this;
}
template <class T> inline void kout::put(T *arr, int num, char dlm, char end) {
  --num;
  for (int i = 0; i < num; ++i)
    (*this) < arr[i] < dlm;
  (*this) < arr[num] < end;
  return;
}