POJ2365【几何】

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因为给出的点已经是顺时针了，
整个长度=相邻点距离+一个圆周长；
C++ac代码…G++wa…因为标准不一样。G++用f

//#include <bits/stdc++.h>#include<iostream>#include<math.h>#include<string.h>#include<cstdio>#include<algorithm>using namespace std;const double pi=acos(double(-1));const int N=1e2+10;double x[N],y[N];int main(){    int n;    double r,len;    while(~scanf("%d%lf",&n,&r))    {        len=0;        for(int i=1;i<=n;i++)        {            scanf("%lf%lf",&x[i],&y[i]);            if(i>=2)            {                if(i!=n)                    len+=sqrt((x[i]-x[i-1])*(x[i]-x[i-1])+(y[i]-y[i-1])*(y[i]-y[i-1]));                else                {                    len+=sqrt((x[i]-x[i-1])*(x[i]-x[i-1])+(y[i]-y[i-1])*(y[i]-y[i-1]));                    len+=sqrt((x[i]-x[1])*(x[i]-x[1])+(y[i]-y[1])*(y[i]-y[1]));                }            }        }        len+=2*pi*r;        printf("%.2lf\n",len);    }    return 0;}

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