#include<stdio.h>
#include<math.h>
#define N 100
#define PI 3.141592653589

struct point
{
	double a, b;
};

double distance(struct point s, struct point t)
{
	return sqrt(pow(s.a-t.a, 2) + pow(s.b-t.b, 2));
}

int main()
{
	int M, i;
	double redium;
	struct point value[N];	
	double sum;
	
	while (fscanf(stdin, "%d %lf", &M, &redium) != EOF)
	{
		sum = 2 * PI * redium;
		
		fscanf(stdin, "%lf %lf", &value[0].a, &value[0].b);
		for (i=1; i<M; i++)
		{
			fscanf(stdin, "%lf %lf", &value[i].a, &value[i].b);
			sum += distance(value[i], value[i-1]);
		}
		sum += distance(value[i-1], value[0]);
		
		printf("%.2lf\n", sum);
	}
	
	return 0;
}

• 只保留第一个点和上一个点就够了，开什么数组 (2) Eov_Second 2016-12-03 00:12:53