实现字符串反转的函数

给定字符串“Hello World”,反序输出“dlroW olleH”。

1、char * strReversed_1(char * dest, char * str)

char * strReversed_1(char * dest, char * str)
{
unsigned int i, j;
if (dest == NULL || str == NULL)
{
return NULL;
}

unsigned int len = strlen(str);

for (i = 0, j = 0; i < len; i++, j++)
{
dest[j] = str[len - i - 1];
}
dest[j] = '\0';

return dest;
}

2、char * strReversed_2(char * str)

char * strReversed_2(char * str)
{
unsigned int i;
if (str == NULL)
{
return NULL;
}

unsigned int len = strlen(str);
char tem;
for (i = 0; i < len / 2; i++)
{
tem = str[i];
str[i] = str[len - i - 1];
str[len - i - 1] = tem;
}

return str;
}

3、char * strReversed_3(char * str)

char * strReversed_3(char * str)
{
unsigned int i;
if (str == NULL)
{
return NULL;
}

unsigned int len = strlen(str);
char * temp = str + len - 1;
char tem;
for (i = 0; i < len / 2; i++)
{
tem = *str;
*str = *temp;
*temp = tem;
*str++;
*temp--;
}

return str - len / 2;
}

验证程序：

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

#define MAX_LEN 64

int main()
{
char strScr[MAX_LEN] = "Hello World";
char strDest[MAX_LEN];

printf("%s\n", strReversed_1(strDest, strScr));
printf("%s\n", strReversed_2(strDest));
printf("%s\n", strReversed_3(strDest));

return 0;
}

输出结果：