UVa 11437 - Triangle Fun

最新推荐文章于 2020-09-18 19:33:33 发布

ACM2272902662

最新推荐文章于 2020-09-18 19:33:33 发布

阅读量2.6k

点赞数 1

CC 4.0 BY-SA版权

分类专栏： UVa

本文链接：https://blog.youkuaiyun.com/yongxingao/article/details/23975219

UVa 专栏收录该内容

75 篇文章

订阅专栏

本文介绍了一种使用向量来确定三角形顶点坐标并计算其面积的方法。通过定义特定的向量和直线方程，实现了由三个点构成的三角形面积的计算。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

该学一下用向量求交点坐标了。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
#include <cmath>
#define eqs 1e-8
using namespace std;
double a = 2.0/3;
double b = 1.0/3;
int main()
{
    //freopen("data.txt","r",stdin);
    double xax,xay;
    double xbx,xby;
    double xcx,xcy;
    double xfx,xfy;
    double xex,xey;
    double xdx,xdy;
    double xpx,xpy;
    double xqx,xqy;
    double xrx,xry;
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf %lf",&xax,&xay);
        scanf("%lf %lf",&xbx,&xby);
        scanf("%lf %lf",&xcx,&xcy);
        xfx = a*xbx+b*xax; xfy = a*xby+b*xay;
        xex = a*xax+b*xcx; xey = a*xay+b*xcy;
        xdx = a*xcx+b*xbx; xdy = a*xcy+b*xby;
        double linadk,linadb;
        int sumad=0;
        if(fabs(xax-xdx-0)<=eqs)
        {
            linadb = xax;
            sumad = 0;
        }else if(fabs(xay-xdy-0)<=eqs)
        {
            linadb = xay;
            sumad = 1;
        }else
        {
            sumad = 2;
            linadk = (xay-xdy)/(xax-xdx);
            linadb = xay - linadk * xax;
        }
        double linfck,linfcb;
        int sumfc=0;
        if(fabs(xfx-xcx-0)<=eqs)
        {
            linfcb = xfx;
            sumfc = 0;
        }else if(fabs(xfy-xcy-0)<=eqs)
        {
            linfcb = xay;
            sumfc = 1;
        }else
        {
            sumfc = 2;
            linfck = (xfy-xcy)/(xfx-xcx);
            linfcb = xfy - linfck * xfx;
        }
        double linbek,linbeb;
        int sumbe=0;
        if(fabs(xbx-xex-0)<=eqs)
        {
            linbeb = xbx;
            sumbe = 0;
        }else if(fabs(xby-xey-0)<=eqs)
        {
            linbeb = xby;
            sumbe = 1;
        }else
        {
            sumbe = 2;
            linbek = (xby-xey)/(xbx-xex);
            linbeb = xby - linbek * xbx;
        }
        if(sumfc==0)
        {
            xrx = linfcb;
            if(sumad==1)
            {
                xry = linadb;
            }else if(sumad==2)
            {
                xry = linadk*xrx+linadb;
            }
            xqx = linfcb;
            if(sumbe==1)
            {
                xqy = linbeb;
            }else if(sumbe==2)
            {
                xqy = linbek*xqx+linbeb;
            }
        }else if(sumfc==1)
        {
            xry = linfcb;
            if(sumad==0)
            {
                xrx = linadb;
            }else if(sumad==2)
            {
                xrx = (xry-linadb)/linadk;
            }
            xqy = linfcb;
            if(sumbe==0)
            {
                xqx = linbeb;
            }else if(sumbe==2)
            {
                xqx = (xqy-linbeb)/linbek;
            }
        }else
        {
            if(sumad==0)
            {
                xrx = linadb;
                xry = xrx*linfck+linfcb;
            }else if(sumad==1)
            {
                xry = linadb;
                xrx = (xry-linfcb)/linfck;
            }else if(sumad==2)
            {
                xrx = (linfcb-linadb)/(linadk-linfck);
                xry = linfck * xrx + linfcb;
            }
            if(sumbe==0)
            {
                xqx = linbeb;
                xqy = xqx*linfck+linfcb;
            }else if(sumbe==1)
            {
                xqy = linbeb;
                xqx = (xqy-linfcb)/linfck;
            }else if(sumad==2)
            {
                xqx = (linfcb-linbeb)/(linbek-linfck);
                xqy = linfck * xqx + linfcb;
            }
        }
        if(sumbe==0)
        {
            xpx = linbeb;
            if(sumad==1)
            {
                xpy = linadb;
            }else if(sumad==2)
            {
                xpy = linadk*xpx+linadb;
            }
        }else if(sumbe==1)
        {
            xpy = linbeb;
            if(sumad==0)
            {
                xpx = linadb;
            }else if(sumad==2)
            {
                xpx = (xpy-linadb)/linadk;
            }
        }else if(sumbe==2)
        {
            if(sumad==0)
            {
                xpx = linadb;
                xpy = xrx*linbek+linbeb;
            }else if(sumad==1)
            {
                xpy = linadb;
                xpx = (xry-linbeb)/linbek;
            }else if(sumad==2)
            {
                xpx = (linbeb-linadb)/(linadk-linbek);
                xpy = linbek * xpx + linbeb;
            }
        }
        double ans = 0;
        ans+=(xpx*xqy-xpy*xqx);
        ans+=(xqx*xry-xqy*xrx);
        ans+=(xrx*xpy-xry*xpx);
        if(ans<0)
        {
            ans = ans * -1;
        }
        ans = ans/2;
        printf("%.0lf\n",ans);
    }
    return 0;
}