C：函数：功能：实现字符数组中所有字母的倒序存放并输出

前两天小测碰到一道题，建立一个函数，功能：实现字符数组中所有字母的倒序存放并输出，一开始觉得简单跟数字数组差不多，运行一下发现很多格式错误，这些是不必要的错误，现在就来说下，先说一下代码思路：定义一个字符数组假如有n个字符，让一个指针变量*p指向首地址，*(p+n-1)就是末地址，然后实现*p与*(p+n-1)值的互换，这边让*q=*(p+n-1)每换一次，p++,q--，当p>q时退出循环,我们来看下代码：

 #include "stdio.h"
 char change(char *p,int y);
 void main()
 {
     char a[]="abcdef";
     change(a,);
     printf("%s",a);
 }
 char change(char *p,int y)
 {
     char *q;
     int temp;//这边比较容易错，有的定性思维，会定义成char类型；
     q=p+y-;
     while(p<q)
     {
         temp=*p;
         *p=*q;
         *q=temp;
         p++;
         q--;
         }
 }

这边只是令n=6,看的更清晰一点，要复杂一点的话，我们也可以自己输入字母，想要几个就几个，这次我用gets()来输入，假如输入n个，那我们怎么知道这个n的值，我们可以先定义*p1让p=a,既指向首地址,要是超过末地址也就是*(p+n)==0,这就给我们一个结束循环的条件：

#include "stdio.h"
void main()
{
    char a[];
    gets(a);
    char *p;
    int i,n;
    i=;
    p=a;
    while(*(p+i)!=)
    {
        i++;

    }
    n=i;
    printf("%d",n);
}

上面代码可以求出我们手动输入字母的个数再加上change()函数就可以了：

#include "stdio.h"
char change(char *p,int y);
void main()
{
    char a[];
    printf("input letter:\n");
    gets(a);
    char *p1;
    int i,n;
    i=;
    p1=a;
    while(*(p1+i)!=)//超出地址结果为0
    {
        i++;
    }
    n=i;
    change(a,n);
    printf("output:\n%s",a);
}
char change(char *p,int y)
{
    char *q;
    int temp;
    q=p+y-;
    while(p<q)
    {
        temp=*p;
        *p=*q;
        *q=temp;
        p++;
        q--;
        }
}

运行结果：aaarticlea/png;base64,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" alt="" />，要是数字数组的话也是差不多的。