获取C语言中的最大值(正无穷)与最小值(负无穷)的一些方法与技巧
在很多的算法题目中经常会遇见设置一个边界状态，如正无穷，负无穷等。在此，也总结了一些方法和技巧供大家参考
1:直接利用计算机的编码特点:
#include
int main(){
printf("INT_MAX = %d\n",unsigned(-1)>>1); //编译器默认-1为int型，所以在转换为unsigned型后并右移一位中，最高位也要随之移动。
printf("-INT_MAX = %d\n",-(unsigned(-1)>>1)-1); //由于计算机采用的补码方式存储，所以对于int型的最小值则为-2^31，也即 -INT_MAX-1。
printf("UNSIGNED_INT_MAX = %u\n",unsigned(-1)); //由于-1的补码的二进制位全为1。所以unsigned(-1)的编码为全1状态的无符号的值。也即无符号的最大值。
return 0;
}
2:利用编译器自带的头文件
/*
C语言中的整数类型
int 是 C 语言的基本整数类型，可以满足我们处理一般数据的需求。
C 语言还提供了四个可以修饰 int 的关键字：short、long、signed，以及 unsigned。
利用这四个关键字，C 语言标准定义了以下整数类型：
1) short int（可简写为 short），和 int 一样，也是有符号整数
2) long int（简写：long），有符号整数
3) long long int（简写：long long），C99标准添加的类型，有符号整数
4) unsigned int（简写：unsigned），无符号整数，不能表示负数
5) unsigned long int（简写：unsigned long），无符号整数，不能表示负数
6) unsigned short int（简写：unsigned short），无符号整数，不能表示负数
7) unsigned long long int（简写：unsigned long long），C99添加的类型，无符号整数
8) 所有没有标明 unsigned 的整数类型默认都是有符号整数。
在这些整数类型前面加上 signed 可以使读者更清楚地知道
这些是有符号整数，尽管有没有 signed 都表示有符号整数。
例如：signed int 等同于 int 。
注意：C语言只规定short <= int <=long int。具体还得看具体的编译器，long int型并不能肯定就是64位的，很多时候long int和int表示的范围是一致的。
一般我们把 short 称为短整型，把 long 称为长整型，把 long long 称为超长整型，把 int 称为整型。unsigned 打头的那些整数类型统称为无符号整型。
例如：我们称 unsigned short 为无符号短整型。以此类推。
*/#include
#include
int main(){
printf("INT_MAX = %d(2*10^10)\n",INT_MAX); //括号内为大约的级数
printf("INT_MIN = %d(-2*10^10)\n",INT_MIN);
printf("UINT_MAX = %u(4*10^10)\n",UINT_MAX);
printf("LONG_LONG_MAX = %lld(9*10^19)\n",LLONG_MAX);
printf("LONG_LONG_MIN = %lld(-9*10^19)\n",LLONG_MIN);
printf("UNSIGNED_LONG_LONG_MAX = %llu(1*10^20)\n",ULONG_LONG_MAX);
return 0;
} 3:扩展:GCC编译器中limits头文件:
/**
* @file limits.h
* Copyright 2012, 2013 MinGW.org project
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef _LIMITS_H
#define _LIMITS_H
#pragma GCC system_header
#include <_mingw.h>
/*
* Functions for manipulating paths and directories (included from io.h)
* plus functions for setting the current drive.
*
* Defines constants for the sizes of integral types.
*
* NOTE: GCC should supply a version of this header and it should be safe to
* use that version instead of this one (maybe safer).
*/
/*
* File system limits
*
* TODO: NAME_MAX and OPEN_MAX are file system limits or not? Are they the
* same as FILENAME_MAX and FOPEN_MAX from stdio.h?
* NOTE: PATH_MAX is the POSIX equivalent for Microsoft's MAX_PATH; the two
* are semantically identical, with a limit of 259 characters for the
* path name, plus one for a terminating NUL, for a total of 260.
*/
# define PATH_MAX 260
/*
* Characteristics of the char data type.
*
* TODO: Is MB_LEN_MAX correct?
*/
#define CHAR_BIT 8
#define MB_LEN_MAX 2
#define SCHAR_MIN (-128)
#define SCHAR_MAX 127
#define UCHAR_MAX 255
#ifndef _CHAR_UNSIGNED
#define CHAR_MIN SCHAR_MIN
#define CHAR_MAX SCHAR_MAX
#else
#define CHAR_MIN 0
#define CHAR_MAX UCHAR_MAX
#endif
/*
* Maximum and minimum values for ints.
*/
#define INT_MAX 2147483647
#define INT_MIN (-INT_MAX-1)
#define UINT_MAX 0xffffffff
/*
* Maximum and minimum values for shorts.
*/
#define SHRT_MAX 32767
#define SHRT_MIN (-SHRT_MAX-1)
#define USHRT_MAX 0xffff
/*
* Maximum and minimum values for longs and unsigned longs.
*/
#define LONG_MAX 2147483647L
#define LONG_MIN (-LONG_MAX-1)
#define ULONG_MAX 0xffffffffUL
#define SSIZE_MAX LONG_MAX
#define LLONG_MAX 9223372036854775807LL
#define LLONG_MIN (-LLONG_MAX - 1)
#define ULLONG_MAX (2ULL * LLONG_MAX + 1)
#define LONG_LONG_MAX 9223372036854775807LL
#define LONG_LONG_MIN (-LONG_LONG_MAX-1)
#define ULONG_LONG_MAX (2ULL * LONG_LONG_MAX + 1)
/* MSVC compatibility */
#define _I64_MIN LONG_LONG_MIN
#define _I64_MAX LONG_LONG_MAX
#define _UI64_MAX ULONG_LONG_MAX
#endif /* not _LIMITS_H */