Misc C++ STL Stuff

• Max Optimisations

#pragma GCC optimize("Ofast","inline","fast-math","unroll-loops","no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native","f16c")

static auto _ = [] () {ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();

• Faster I/O

  #pragma GCC optimize("Ofast")
  static auto _ = [] () {ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();
  

• max element in a container

  vector<int> vec;
  auto it = max_element(vec.begin(), vec.end());
    
  int ans = *it;
  

• <limits.h> is pretty useful

CONSTANT	SIZE	DESCRIPTION
CHAR_BIT	8	Defines the number of bits in a byte.
SCHAR_MIN	-128	Defines the minimum value for a signed char.
SCHAR_MAX	+127	Defines the maximum value for a signed char.
UCHAR_MAX	255	Defines the maximum value for an unsigned char.
CHAR_MIN	-128	Defines the minimum value for type char and its value will be equal to SCHAR_MIN if char represents negative values, otherwise zero.
CHAR_MAX	+127	Defines the value for type char and its value will be equal to SCHAR_MAX if char represents negative values, otherwise UCHAR_MAX.
MB_LEN_MAX	16	Defines the maximum number of bytes in a multi-byte character.
SHRT_MIN	-32768	Defines the minimum value for a short int.
SHRT_MAX	+32767	Defines the maximum value for a short int.
USHRT_MAX	65535	Defines the maximum value for an unsigned short int.
INT_MIN	-2147483648	Defines the minimum value for an int.
INT_MAX	+2147483647	Defines the maximum value for an int.
UINT_MAX	4294967295	Defines the maximum value for an unsigned int.
LONG_MIN	-9223372036854775808	Defines the minimum value for a long int.
LONG_MAX	+9223372036854775807	Defines the maximum value for a long int.
ULONG_MAX	18446744073709551615	Defines the maximum value for an unsigned long int.

  cout << INT_MAX << INT_MIN;

• Setting an int to infinity

  #include <limits>
    
  int a = std::numeric_limits<int>::max();
  float b = std::numeric_limits<float>::infinity();
  

• Checking if your system is little endian or big endian ```c++ #define BIG_ENDIAN 0 #define LITTLE_ENDIAN 1

int TestByteOrder() { short int word = 0x0001; char *byte = (char *)&word; return (byte[0] ? LITTLE_ENDIAN : BIG_ENDIAN); } ```