各位，问一下这要怎么写？

可以看看这个https://www.cnblogs.com/lemaden/p/10120660.html

代码如下：

#include <iostream>

using namespace std;
void fun(char* s)
{
	int len=0;
	int i,j;
	char ch;
	while(s[len]!='\0')
		len++;
	for (i=0,j=len-1;i<j;i++,j--)
	{
		ch = s[j];
		s[j] = s[i];
		s[i] = ch;
	}
}

int main()
{
	char buf[100] = {0};
	cin >> buf;
	fun(buf);
	cout << buf <<endl;
	return 0;
}