不开辟用于交换数据的临时空间，如何完成字符串的逆序

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

void reverse(char *str)
{
int len = strlen(str),i = 0,j = len-1;
while(i < j)
{
str[i] ^= str[j] ^= str[i] ^= str[j];
i++;
j--;
}
}

int main()
{
char str[30];
printf("请输入字符串\n");
scanf("%s",str);
reverse(str);
printf("%s\n", str);
}

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

void reverse(char *str)
{
int len = strlen(str),i = 0,j = len-1;
while(i < j)
{
str[len] = str[i];
str[i] = str[j];
str[j] = str[len];
i++;
j--;
}
str[len] = '\0';
}

int main()
{
char str[30];
printf("请输入字符串\n");
scanf("%s",str);
reverse(str);
printf("%s\n", str);
}