这道题用很多个if判断就行了！

#include <bits/stdc++.h>
using namespace std;
int main()
{
  	float a,b,c;
  	cin >> a >> b >> c;
	if(a < b && b < c)
		cout << a << " " << b << " " << c;
	if(a < c && c < b)
		cout << a << " " << c << " " << b;
	if(b < a && a < c)
		cout << b << " " << a << " " << c;
	if(b < c && c < a)
		cout << b << " " << c << " " << a;
	if(c < b && b < a)
		cout << c << " " << b << " " << a;
	if(c < a && a < b)
		cout << c << " " << a << " " << b;
  	return 0;
}