#include <iostream>
#include <math.h>
using namespace std;
int main(){                                                           
 int a,b,c;
 cin >> a >> b >> c;
 
 if( pow(c,2) ==pow(a,2) + pow(b,2))
  {
   cout << "right triangle" << endl;
  }
 

 else if( pow(c,2) < pow(a,2) + pow(b,2))
 {
  cout<<"acute triangle"<<endl;
 }
        else if( pow(c,2) > pow(a,2) + pow(b,2))
  {
   cout << "obtuse triangle" << endl;
  }
 else
 {
  cout << "no answer" << endl;
 }
 return 0;
}

他說題目競賽中，我看不到題目

但我猜abc大小不固定？

先排序？

我在猜啦，畢竟看不到題目

#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
	int array[4];
	int buffer;
	while (cin >> array[1] >> array[2] >> array[3])
	{
		//排序
		for (int i = 1; i <= 2; i++)
			for (int j = 2; j <= 3; j++)
				if (array[j] < array[i])
				{
					buffer = array[i];
					array[i] = array[j];
					array[j] = buffer;
				}
		int a = array[1];
		int b = array[2];
		int c = array[3];
		if (a * a + b * b == c * c)
			cout << "right triangle" << endl;
		else if (a * a + b * b < c * c)
			cout << "obtuse triangle" << endl;
		else if (a * a + b * b > c * c)
			cout << "acute triangle" << endl;
	}
	//system("PAUSE");
	return 0;
}

附上無排序版本：

#include <cstdio>
#define max(x,y,z) x>y && x>z?x:(y>z?y:z)

using namespace std;


int main(){
    int a,b,c,mx;
    while(scanf("%d%d%d",&a,&b,&c)!=EOF){
        mx=max(a,b,c);
        mx=mx*mx*2,a*=a,b*=b,c*=c;
        if(mx==a+b+c)printf("right triangle\n");
        else if(mx>a+b+c)printf("obtuse triangle\n");
        else printf("acute triangle\n");
    }

    return 0;
}

其實只要a b c 分開輸入，並在每一次輸入完後比較大小就好。

不需要沒事寫這很做作的東西 ---> x>y && x>z?x:(y>z?y:z)