HDU 4386 Quadrilateral 简单几何
#include <set>#include <map>#include <list>#include <cmath>#include <ctime>#include <deque>#include <queue>#include <stack>#include <cctype>#include <cstdio>#include <string>#include <vector>#include <cassert>#include <cstdlib>#include <cstring>#include <sstream>#include <iostream>#include <algorithm>using namespace std;int max(int a,int b){return a<b?b:a;}int min(int a,int b){return a>b?b:a;}int main(){int cas,t=1;cin>>cas;while(cas--){double a,b,c,d;{cin>>a>>b>>c>>d;bool f=1;double s=(a+b+c+d)/2;double ans=sqrt((s-a)*(s-b)*(s-c)*(s-d));if(a>=b+c+d || b>=a+c+d || c>=a+b+d || d>=a+b+c)printf("Case %d: -1\n",t++);else printf("Case %d: %.6lf\n",t++,ans);}}return 0;}详细证明 : http://www.doc88.com/p-792551521271.html
具体就是海伦公式水过