字符串逆序打印

版本1 两个指针从头到尾和从尾到头交换内容逆序

/***
str_reverse.c
***/
#include<stdio.h>
#include<string.h>

int main()
{
    char buf[] = "abcdrfg";

    int len = strlen(buf);
    char *p1 = buf;
    char *p2 = buf + len - 1;

    while(p1 < p2)
    {
        char c = *p1;
        *p1 = *p2;
        *p2 = c;
        ++p1;
        --p2;
    }

    printf("buf = %s\n",buf);
    return 0; 
}

版本2

使用函数接口封装

/***
str_reverse.c
***/

#include<stdio.h>
#include<string.h>

int my_reverse(char *str)
{
    int iRet = -1;
    if(NULL == str)
    {
        return iRet;    
    }
   
    char *buf = str;
    int len = strlen(buf);
    char *p1 = buf;
    char *p2 = buf + len - 1;

    while(p1 < p2)
    {
        char c = *p1;
        *p1 = *p2;
        *p2 = c;
        ++p1;
        --p2;
    }

}

int main()
{
    char buf[] = "abcdrfg";
    my_reverse(buf);

    printf("buf = %s\n",buf);
    return 0; 
}

版本三

使用栈特性将字符串存储到全局变量中

/***
str_reverse.c
***/

#include<stdio.h>
#include<string.h>

char g_buf[256];

void reverse(char *p)
{
    if(NULL == p)
    {
        return ;
    }
    if(*p == '\0')
    {
        return;
    }

    reverse(p+1);
    strncat(g_buf,p,1);
}

int main()
{
    char buf[] = "abcd";
    memset(g_buf,0,sizeof(g_buf));
    reverse(buf);
    printf("g_buf = %s\n",g_buf);
    return 0;
}

版本4

使用栈将字符串存到传入的局部变量中

/***
str_reverse.c
***/

#include<stdio.h>
#include<string.h>

char g_buf[256];

void reverse(char *p)
{
    if(NULL == p)
    {
        return ;
    }
    if(*p == '\0')
    {
        return;
    }

    reverse(p+1);
    strncat(g_buf,p,1);
}

int main()
{
    char buf[] = "abcd";
    memset(g_buf,0,sizeof(g_buf));
    reverse(buf);
    printf("g_buf = %s\n",g_buf);
    return 0;
}