hdu 6857 Clockwise or Counterclockwise

ziyou_zi

于 2020-08-15 17:03:10 发布

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本文链接：https://blog.youkuaiyun.com/weixin_45892201/article/details/108025137

版权

Clockwise or Counterclockwise

原题链接

题意

圆上三点A->B->C是顺时针还是逆时针

思路

求出A,B,C三点所在半径角度数，再比较

#include <queue>
#include <cstdlib>
#include <cmath>
#include <cstdio>
#include <string>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
double s(int x,int y)//返回点所在的半径的角度数 
{
	if(x>0&&y>0)return atan(1.0*y/x);
	else if(x<0&&y>0)return atan(-1.0*x/y)+asin(1);
	else if(x<0&&y<0)return atan(1.0*y/x)+2*asin(1);
	else if(x>0&&y<0)return atan(-1.0*x/y)+3*asin(1);
	else if(x>0&&y==0)return 0;
	else if(x==0&&y>0)return asin(1);
	else if(x<0&&y==0)return 2*asin(1);
	else if(x==0&&y<0)return 3*asin(1);
}
int main()
{
    int t,x1,x2,x3,y1,y2,y3;
    double l1,l2,l3;
    cin>>t;
    while(t--)
    {
    	cin>>x1>>y1>>x2>>y2>>x3>>y3;
    	l1=s(x1,y1);
    	l2=s(x2,y2);
    	l3=s(x3,y3);
    	if(l1>l2)//判断A->B方向是否是顺时针 
    	{
    		if(l3>l2&&l3<l1)printf("Counterclockwise\n");
    		else printf("Clockwise\n");
		}
		else
    	{
    		if(l3>l1&&l3<l2)printf("Clockwise\n");
    		else printf("Counterclockwise\n");
		}
	}
    return 0;
}