【HDOJ5979】Convex（三角函数）

题意：n个点在一个半径为R的圆上，给出这n个点顺时针的夹角差值，求这n个点的凸包面积

n<=10，R<=10

思路：S=1/2*sinθ*a*b

角度转弧度再用sin

C++有点小毛病，叫队友改了下

 #include<cstdio>
 #include<cstring>
 #include<string>
 #include<cmath>
 #include<iostream>
 #include<algorithm>
 #include<map>
 #include<set>
 #include<queue>
 #include<vector>
 using namespace std;
 typedef long long ll;
 typedef unsigned int uint;
 typedef unsigned long long ull;
 typedef pair<int,int> PII;
 typedef vector<int> VI;
 #define fi first
 #define se second
 #define MP make_pair
 #define N   1100000
 #define MOD 1000000007
 #define eps 1e-8
 #define pi  acos(-1)

 int n;
 double L;

 int read()
 {
    int v=,f=;
    char c=getchar();
    while(c<||<c) {if(c=='-') f=-; c=getchar();}
    while(<=c&&c<=) v=(v<<)+v+v+c-,c=getchar();
    return v*f;
 }

 int main()
 {
     while(scanf("%d%lf",&n,&L)!=EOF)
     {
          double ans=;
          for(int i = ; i <= n; ++i)
          {
              double x;
              scanf("%lf",&x);
              x/=*1.0;
              x*=pi*1.0;
              ans+=1.0/*L*L*sin(x);
          }
          printf("%.3lf\n",ans);
     }
     return ;
 }