UVA Problem#438

Question:

http://uva.onlinejudge.org/external/4/438.html 

Solution:

int main(){

.....

.... 

m1= (y2-y1)/(x2-x1); 

m2= (y3-y1)/(x3-x1); 

if (m2==0){

  k= (x2-x3)/m1/2 + (y1+y2)/2; 

h= (x1+x3)/2; }

if (m1==0){

  k=(x3-x2)/m2/2 + (y1+y3)/2; 

h=(x1+x2)/2; 

}

else if (m1!=0&&m2!=0){ 

h= ((x1+x2)/m1 - (x1+x3)/m2 + y2-y3)/2/(1/m1 - 1/m2);

  k= ( h-(x1+x2)/2)/(-m1) + (y1+y2)/2; 

}

r= sqrt((h-x1)*(h-x1) + (k-y1)*(k-y1)); 

ans=2*pi*r;   

......

...

}