码蹄集 精准弹幕

 这里边比较关键的就是对斜率和角度的处理

具体怎么使用查看下面这条链接

cos()_C语言cos()详解：余弦函数，求某个角的余弦值 (biancheng.net)

#include<bits/stdc++.h> 

using namespace std;
#define PI 3.14159265

int main( )
{
    double x,y,r,xt,yt;
    double k;
    cin >> x >> y >> r >> k >> xt >> yt;

    double y1,x1, y2, x2;
    double a;
    a = atan(k)*180/PI;

    a = 90.0-a;

    if(k>0){
        x1 = x+r*cos(a*PI/180);
        y1 = y-r*sin(a*PI/180);  

        x2 = x-r*cos(a*PI/180);  
        y1 = y+r*sin(a*PI/180);

        y1 = k*(xt-x1)+y1;
        y2 = k*(xt-x2)+y2;

        if((y1<=yt and y2>=yt) or(y1>=yt and y2<=yt)){
            cout << 1;
        }
        else{
        	cout << 0;
		}
    }

    if(k<0){
        x1 = x-r*cos(a*PI/180);
        y1 = y-r*sin(a*PI/180);   

        x2 =  x+r*cos(a*PI/180);
        y2 =  y+r*sin(a*PI/180);   

        y1 = k*(xt-x1)+y1;
        y2 = k*(xt-x2)+y2;

        if((y1<=yt and y2>=yt) or (y1>=yt and y2<=yt)){
            cout << 1;
        }
        else{
        	cout << 0;
		}
    }
    
    if(k==0) {
    	if(yt>=y-r and yt <=y+r){
    		cout << 1;
		}
		else{
			cout << 0;
		}
	}
    return 0;
}