LA4356

来源：互联网发布：网络词钵钵鸡什么意思编辑：程序博客网时间：2024/05/16 03:33

la上不去了，给杭电的链接：

http://acm.hdu.edu.cn/showproblem.php?pid=2469

要去上课了，题解先不写了- -

#include <iostream>#include <cmath>#include <algorithm>#include <vector>#include <cstdio>using namespace std;#define pi acos(-1.0)typedef struct point{    int x, y;    int r;    double theta;} p;bool operator <(p a,p b){    return a.theta < b.theta;}int main(){    ios::sync_with_stdio(false);    int N,K;    int count_of_case = 0;    while(cin>>N>>K && (N || K))    {        int t = N;        vector<p> a;        p temp;        while(t--)        {            cin>>temp.x>>temp.y;            temp.r = temp.x*temp.x + temp.y*temp.y;            temp.theta = atan2((double)temp.y,(double)temp.x);            a.push_back(temp);        }        if(!K)        {            printf("Case #%d: 0.00\n",++count_of_case);            continue;        }        sort(a.begin(),a.end());                double ans = 1 << 30;        double angle;        double b[5000];        printf("Case #%d: ",++count_of_case);        for(int i=0; i<N; i++)        {            int n=0;            for(int j=0; j<N; j++)            {                if(a[j].r<=a[i].r)                {                    b[n++]=a[j].theta;                }            }            if(n<K)            {                continue;            }            for(int j=0, k = K - 1; j<n; j++,k++)            {                if(k<n)                {                    angle=b[k]-b[j];                }                else                {                    angle=b[k-n]-b[j]+pi*2;                }                ans=min(ans,.5*angle*a[i].r);            }        }        printf("%.2f\n",ans);    }}