整理库函数，头文件——C

（一）、

#include <stdio.h>
#include <assert.h>

int main(void)
{

        //若assert(expression)中表达式是错误的，则直接退出。
    int a;
    char str[50];
    printf(":");
    scanf("%d", &a);
    assert(a >= 10);
    printf(":%d\n", a);

    printf(":");
    scanf("%s", str);
    assert(str != NULL);
    printf(":%s\n", str);
    return 0;
}

（二）、ctype.h

//isalpha判断是字母,islower小写字母，isupper大写字母，istoupper转化大写，istolower转化小写。

#include <stdio.h>
#include <ctype.h>

int main()
{
   int var1 = &#39;d&#39;;
   int var2 = &#39;2&#39;;
   int var3 = &#39;\t&#39;;
   int var4 = &#39; &#39;;
   if( isalpha(var1) )
   {
      printf("var1 = |%c| 是一个字母\n", var1 );
   }
   else
   {
      printf("var1 = |%c| 不是一个字母\n", var1 );
   }
   if( isalpha(var2) )
   {
      printf("var2 = |%c| 是一个字母\n", var2 );
   }
   else
   {
      printf("var2 = |%c| 不是一个字母\n", var2 );
   }
   if( isalpha(var3) )
   {
      printf("var3 = |%c| 是一个字母\n", var3 );
   }
   else
   {
      printf("var3 = |%c| 不是一个字母\n", var3 );
   }
   if( isalpha(var4) )
   {
      printf("var4 = |%c| 是一个字母\n", var4 );
   }
   else
   {
      printf("var4 = |%c| 不是一个字母\n", var4 );
   }
   return(0);
}

（三）、limits.h

#include <stdio.h>
#include <limits.h>

//注意INT_MIN和INT_MAX多应用于比较大小。

int main()
{

   printf("The number of bits in a byte %d\n", CHAR_BIT);

   printf("The minimum value of SIGNED CHAR = %d\n", SCHAR_MIN);
   printf("The maximum value of SIGNED CHAR = %d\n", SCHAR_MAX);
   printf("The maximum value of UNSIGNED CHAR = %d\n", UCHAR_MAX);

   printf("The minimum value of SHORT INT = %d\n", SHRT_MIN);
   printf("The maximum value of SHORT INT = %d\n", SHRT_MAX); 

   printf("The minimum value of INT = %d\n", INT_MIN);
   printf("The maximum value of INT = %d\n", INT_MAX);

   printf("The minimum value of CHAR = %d\n", CHAR_MIN);
   printf("The maximum value of CHAR = %d\n", CHAR_MAX);

   printf("The minimum value of LONG = %ld\n", LONG_MIN);
   printf("The maximum value of LONG = %ld\n", LONG_MAX);

   return(0);
}

#include <stdio.h>
#include <limits.h>

//https://vjudge.net/contest/338668#problem/H
int main(void)
{

    int n,a,s,max,min,sum;
    int d[100+1];
    double agv;

    while(~scanf("%d",&n)){

        for(a = 0; a < n; a++)
            scanf("%d", &d[a]);
            sum = 0;
            agv = 0.0;
        max = INT_MIN;
        min = INT_MAX;
        for(s=0; s < n; s++){
            if(max < d[s])
                max = d[s];
            if(min > d[s])
                min = d[s];
        }
        for(s=0; s < n; s++)
            sum += d[s];
        agv = (double)(sum-max-min) / (n-2);
        printf("%.2lf\n", agv);
    }
    return 0;
}