C++(g++ 7.5.0) 解法, 执行用时: 373ms, 内存消耗: 504K, 提交时间: 2023-01-04 16:12:50

#include<bits/stdc++.h>
using namespace std;
const double PI = acos(-1.0);
double f(double x1,double y1,double x2,double y2)
{
    return sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
}

int main()
{
	double r;
	double x1,x2,y1,y2;
	cin>>r;
	cin>>x1>>y1>>x2>>y2;
	
	double ans = f(x1,y1,x2,y2);
	
	for(double i=0;i<2*PI;i+=0.000001)
	{
		double x3 = r * cos(i);
		double y3 = r * sin(i);
		
		ans = min(ans,f(x1,y1,x3,y3) + f(-x2,-y2,x3,y3));
	}
	
	printf("%.12lf\n",ans);
	
	return 0;
}

C++ 解法, 执行用时: 24ms, 内存消耗: 452K, 提交时间: 2022-01-05 16:24:43

#include<bits/stdc++.h>
using namespace std;
#define PI acos(-1.0)
double r,a,b,c,d;
int main()
{
  double i,ans;
  scanf("%lf%lf%lf%lf%lf",&r,&a,&b,&c,&d);
  ans=sqrt((a-c)*(a-c)+(b-d)*(b-d));
  for(i=0;i<=360;i+=1e-3)
  {
    double xx,yy,res;
    xx=r*cos(i*PI/180);
    yy=r*sin(i*PI/180);
    res=sqrt((c-xx)*(c-xx)+(d-yy)*(d-yy))+sqrt((a+xx)*(a+xx)+(b+yy)*(b+yy));
    if(ans>res)
        ans=res;
  }
  printf("%.12f",ans);
  return 0;
}