一月24日新生冬季练习赛解题报告D.三角形面积

水的离谱：

啊啊啊啊啊啊

已知三边求面积可以：

#include<iostream>

#include<string.h>

#include<stdio.h>

#include<queue>

#include<stack>

#include<map>

#include<vector>

#include<cmath>

#include<iomanip>

using namespace std;

struct point

{

double x;

double y;

}poin[101];

int main()

{

int t;

cin>>t;

while(t--)

{

cin>>poin[0].x>>poin[0].y>>poin[1].x>>poin[1].y>>poin[2].x>>poin[2].y;

double a=sqrt(pow((poin[0].x-poin[1].x)*1.0,2.0)+(pow((poin[0].y-poin[1].y)*1.0,2.0)));

double b=sqrt(pow((poin[0].x-poin[2].x)*1.0,2.0)+(pow((poin[0].y-poin[2].y)*1.0,2.0)));

double c=sqrt(pow((poin[2].x-poin[1].x)*1.0,2.0)+(pow((poin[2].y-poin[1].y)*1.0,2.0)));

if(a+b>c&&a+c>b&&b+c>a)

{

double d=0.5*(a+b+c);

double s=sqrt(d*(d-a)*(d-b)*(d-c));

cout<<setprecision(2)<<std::fixed<<s<<endl;

}

else

cout<<"fail"<<endl;

}

return 0;

}

茶几也可以：

#include<iostream>

#include<string.h>

#include<stdio.h>

#include<queue>

#include<stack>

#include<map>

#include<vector>

#include<cmath>

#include<iomanip>

using namespace std;

#define minn 1e-8

struct point

{

double x;

double y;

}poin[101];

double cross(point p1,point p0,point p2)

{

return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p1.y);

}

int main()

{

int t;

cin>>t;

while(t--)

{

cin>>poin[0].x>>poin[0].y>>poin[1].x>>poin[1].y>>poin[2].x>>poin[2].y;

double ans=cross(poin[1],poin[0],poin[2]);

if(ans<=minn&&ans+minn>=0)

cout<<"no"<<endl;

else

cout<<ans/2<<endl;

}

return 0;

}