Hello, Codeforces!
I'm excited to share my C++ library that can significantly improve the performance of your solutions, especially when dealing with large input and output.
https://github.com/alexmcmahonsoftware/fast-io
Code
#include <algorithm>
#include <cctype>
#include <cstdio>
#include <cstring>
#include <stack>
#include <string>
using namespace std;
class fistream
{
public:
static const int bufsz = 1 << 16;
class buffer
{
public:
int isz;
char ibuf[bufsz];
};
FILE * pin;
stack<buffer> ibuf_stk;
int ipt, isz;
char ibuf[bufsz];
char word[64];
fistream();
fistream(FILE *);
operator bool ();
void stack_buffer();
void next_buffer();
bool trim();
bool integral();
bool floating();
bool getline(char *, const int &);
bool eof();
void putback(const char &);
fistream & operator >> (char &);
fistream & operator >> (char *);
fistream & operator >> (int &);
fistream & operator >> (unsigned int &);
fistream & operator >> (long long &);
fistream & operator >> (unsigned long long &);
fistream & operator >> (__int128 &);
fistream & operator >> (unsigned __int128 &);
fistream & operator >> (float &);
fistream & operator >> (double &);
fistream & operator >> (long double &);
} fin(stdin), fin_null(0);
fistream::fistream() : pin(0), ipt(bufsz), isz(bufsz)
{
}
fistream::fistream(FILE * pin) : pin(pin), ipt(bufsz), isz(bufsz)
{
}
inline fistream::operator bool ()
{
return this != &fin_null;
}
inline void fistream::stack_buffer()
{
if (ipt == 0)
{
ibuf_stk.push(buffer());
ibuf_stk.top().isz = isz;
memcpy(ibuf_stk.top().ibuf, ibuf, sizeof ibuf[0] * isz);
isz = bufsz;
ipt = isz;
}
}
inline void fistream::next_buffer()
{
if (ibuf_stk.empty())
isz = fread(ibuf, 1, bufsz, pin);
else
{
isz = ibuf_stk.top().isz;
memcpy(ibuf, ibuf_stk.top().ibuf, sizeof ibuf[0] * isz);
ibuf_stk.pop();
}
ipt = 0;
}
inline bool fistream::trim()
{
for (; isz > 0; next_buffer())
{
for (; ipt < isz && ibuf[ipt] <= ' '; ipt++);
if (ipt < isz)
break;
}
return eof();
}
inline bool fistream::integral()
{
if (trim())
return false;
int len = 0;
bool vld = false;
if (ibuf[ipt] == '-' || ibuf[ipt] == '+')
word[len++] = ibuf[ipt++];
for (; isz > 0; next_buffer())
{
for (; ipt < isz && isdigit(ibuf[ipt]); ipt++)
{
word[len++] = ibuf[ipt];
vld = true;
}
if (ipt < isz)
break;
}
word[len] = 0;
return vld;
}
inline bool fistream::floating()
{
if (trim())
return false;
int len = 0;
bool vld = false, rht = false;
if (ibuf[ipt] == '-' || ibuf[ipt] == '+')
word[len++] = ibuf[ipt++];
for (; isz > 0; next_buffer())
{
for (; ipt < isz && (isdigit(ibuf[ipt]) || ibuf[ipt] == '.'); ipt++)
{
if (ibuf[ipt] == '.')
{
if (rht)
break;
else
rht = true;
}
else
vld = true;
word[len++] = ibuf[ipt];
}
if (ipt < isz)
break;
}
word[len] = 0;
return vld;
}
inline bool fistream::getline(char * s, const int & n)
{
if (this == &fin_null || eof())
return false;
int slen = 0;
for (; isz > 0; next_buffer())
{
for (; ipt < isz && slen < n - 1 && ibuf[ipt] != '\n'; ipt++)
s[slen++] = ibuf[ipt];
if (ipt < isz)
break;
}
s[slen] = 0;
for (; isz > 0 && ipt == isz; next_buffer());
if (ipt < isz && ibuf[ipt] == '\n')
ipt++;
return true;
}
inline bool fistream::eof()
{
for (; isz > 0 && ipt == isz; next_buffer());
return isz == 0;
}
inline void fistream::putback(const char & c)
{
if (ipt == 0)
stack_buffer();
ibuf[--ipt] = c;
}
inline fistream & fistream::operator >> (char & c)
{
if (this == &fin_null || trim())
return fin_null;
else
{
c = ibuf[ipt++];
return *this;
}
}
inline fistream & fistream::operator >> (char * s)
{
if (this == &fin_null || trim())
return fin_null;
int slen = 0;
for (; isz > 0; next_buffer())
{
for (; ipt < isz && ibuf[ipt] > ' '; ipt++)
s[slen++] = ibuf[ipt];
if (ipt < isz)
break;
}
s[slen] = 0;
return *this;
}
inline fistream & fistream::operator >> (int & x)
{
if (this == &fin_null || !(this->integral()))
return fin_null;
int i = 0, sgn;
int ans = 0;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
ans = ans * 10 + word[i] - '0';
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (unsigned int & x)
{
if (this == &fin_null || !(this->integral()))
return fin_null;
int i = 0, sgn;
int ans = 0;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
ans = ans * 10 + word[i] - '0';
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (long long & x)
{
if (this == &fin_null || !(this->integral()))
return fin_null;
int i = 0, sgn;
long long ans = 0;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
ans = ans * 10 + word[i] - '0';
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (unsigned long long & x)
{
if (this == &fin_null || !(this->integral()))
return fin_null;
int i = 0, sgn;
long long ans = 0;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
ans = ans * 10 + word[i] - '0';
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (__int128 & x)
{
if (this == &fin_null || !(this->integral()))
return fin_null;
int i = 0, sgn;
__int128 ans = 0;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
ans = ans * 10 + word[i] - '0';
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (unsigned __int128 & x)
{
if (this == &fin_null || !(this->integral()))
return fin_null;
int i = 0, sgn;
__int128 ans = 0;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
ans = ans * 10 + word[i] - '0';
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (float & x)
{
if (this == &fin_null || !(this->floating()))
return fin_null;
int i = 0, sgn;
bool vis = false;
float ans = 0, factor = 1;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
{
if (word[i] == '.')
{
vis = true;
continue;
}
if (!vis)
ans = ans * 10 + word[i] - '0';
else
{
factor /= 10;
ans += factor * (word[i] - '0');
}
}
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (double & x)
{
if (this == &fin_null || !(this->floating()))
return fin_null;
int i = 0, sgn;
bool vis = false;
double ans = 0, factor = 1;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
{
if (word[i] == '.')
{
vis = true;
continue;
}
if (!vis)
ans = ans * 10 + word[i] - '0';
else
{
factor /= 10;
ans += factor * (word[i] - '0');
}
}
x = ans * sgn;
return *this;
}
inline fistream & fistream::operator >> (long double & x)
{
if (this == &fin_null || !(this->floating()))
return fin_null;
int i = 0, sgn;
bool vis = false;
long double ans = 0, factor = 1;
if (word[0] == '-')
sgn = -1, i++;
else if (word[0] == '+')
sgn = 1, i++;
else
sgn = 1;
for (; word[i]; i++)
{
if (word[i] == '.')
{
vis = true;
continue;
}
if (!vis)
ans = ans * 10 + word[i] - '0';
else
{
factor /= 10;
ans += factor * (word[i] - '0');
}
}
x = ans * sgn;
return *this;
}
class fostream
{
public:
static const int bufsz = 1 << 16;
FILE * pout;
int opt;
char obuf[bufsz];
char word[64];
int pcs;
string format_float, format_double, format_long_double;
class precision
{
public:
int pcs;
precision() : pcs(0)
{
}
precision(const int & pcs) : pcs(pcs)
{
}
};
fostream();
fostream(FILE *);
~fostream();
void fprecision(const int &);
fostream & operator << (const precision &);
fostream & operator << (const char &);
fostream & operator << (const char *);
fostream & operator << (const int &);
fostream & operator << (const unsigned int &);
fostream & operator << (const long long &);
fostream & operator << (const unsigned long long &);
fostream & operator << (const __int128 &);
fostream & operator << (const unsigned __int128 &);
fostream & operator << (const float &);
fostream & operator << (const double &);
fostream & operator << (const long double &);
void flush();
} fout(stdout), ferr(stderr);
const char fendl = '\n';
fostream::fostream() : pout(0), opt(0), pcs(3), format_float("%.3f"), format_double("%.3lf"), format_long_double("%.3Lf")
{
}
fostream::fostream(FILE * pout) : pout(pout), opt(0), pcs(3), format_float("%.3f"), format_double("%.3lf"), format_long_double("%.3Lf")
{
}
fostream::~fostream()
{
flush();
}
inline void fostream::fprecision(const int & x)
{
pcs = x;
sprintf(word, "%%.%d", pcs);
(format_float = word) += "f";
(format_double = word) += "lf";
(format_long_double = word) += "Lf";
}
inline fostream & fostream::operator << (const precision & rhs)
{
fprecision(rhs.pcs);
return *this;
}
inline fostream & fostream::operator << (const char & c)
{
obuf[opt++] = c;
if (opt == bufsz)
flush();
return *this;
}
inline fostream & fostream::operator << (const char * s)
{
for (int i = 0; s[i]; i++)
{
obuf[opt++] = s[i];
if (opt == bufsz)
flush();
}
return *this;
}
inline fostream & fostream::operator << (const int & x)
{
int len = 0;
unsigned int y;
if (x < 0)
word[len++] = '-', y = -x;
else
y = x;
if (y == 0)
word[len++] = '0';
else
{
for (; y > 0; y /= 10)
word[len++] = '0' + y % 10;
}
reverse(word + (x < 0 ? 1 : 0), word + len);
word[len] = 0;
*this << word;
return *this;
}
inline fostream & fostream::operator << (const unsigned int & x)
{
int len = 0;
if (x == 0)
word[len++] = '0';
else
{
for (unsigned int y = x; y > 0; y /= 10)
word[len++] = '0' + y % 10;
}
reverse(word, word + len);
word[len] = 0;
*this << word;
return *this;
}
inline fostream & fostream::operator << (const long long & x)
{
int len = 0;
unsigned long long y;
if (x < 0)
word[len++] = '-', y = -x;
else
y = x;
if (y == 0)
word[len++] = '0';
else
{
for (; y > 0; y /= 10)
word[len++] = '0' + y % 10;
}
reverse(word + (x < 0 ? 1 : 0), word + len);
word[len] = 0;
*this << word;
return *this;
}
inline fostream & fostream::operator << (const unsigned long long & x)
{
int len = 0;
if (x == 0)
word[len++] = '0';
else
{
for (unsigned long long y = x; y > 0; y /= 10)
word[len++] = '0' + y % 10;
}
reverse(word, word + len);
word[len] = 0;
*this << word;
return *this;
}
inline fostream & fostream::operator << (const __int128 & x)
{
int len = 0;
unsigned __int128 y;
if (x < 0)
word[len++] = '-', y = -x;
else
y = x;
if (y == 0)
word[len++] = '0';
else
{
for (; y > 0; y /= 10)
word[len++] = '0' + y % 10;
}
reverse(word + (x < 0 ? 1 : 0), word + len);
word[len] = 0;
*this << word;
return *this;
}
inline fostream & fostream::operator << (const unsigned __int128 & x)
{
int len = 0;
if (x == 0)
word[len++] = '0';
else
{
for (unsigned __int128 y = x; y > 0; y /= 10)
word[len++] = '0' + y % 10;
}
reverse(word, word + len);
word[len] = 0;
*this << word;
return *this;
}
inline fostream & fostream::operator << (const float & x)
{
sprintf(word, format_float.c_str(), x);
*this << word;
return *this;
}
inline fostream & fostream::operator << (const double & x)
{
sprintf(word, format_double.c_str(), x);
*this << word;
return *this;
}
inline fostream & fostream::operator << (const long double & x)
{
sprintf(word, format_long_double.c_str(), x);
*this << word;
return *this;
}
inline void fostream::flush()
{
if (opt > 0)
{
fwrite(obuf, 1, opt, pout);
opt = 0;
}
}
inline fostream::precision fsetprecision(const int & x)
{
return fostream::precision(x);
}
For years, I've been using this library myself, and it consistently delivers:
Up to 5x faster I/O on average: Solve problems quicker and avoid unnecessary timeouts.
Blazing-fast performance for large data: Notice a 10x speedup for inputs/outputs exceeding 1MB.
But speed isn't everything! This library also prioritizes ease of use:
Seamless integration: Simply replace
cinandcoutwithfinandfoutin your code.Familiar syntax: The library implements standard C++ stream operators for an intuitive experience.
Extended Compatibility: Handles all fundamental data types and offers precision control for floating-point numbers.
I'm confident this library can be a valuable asset for you, especially when dealing with large data. While this is just the first step, stay tuned for future posts where I'll introduce more tools and techniques to help you conquer Codeforces!
Thank you.
