【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

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<string>
 4 #include<cmath>
 5 #include<iostream>
 6 #include<algorithm>
 7 #include<map>
 8 #include<set>
 9 #include<queue>
10 #include<vector>
11 using namespace std;
12 typedef long long ll;
13 typedef unsigned int uint;
14 typedef unsigned long long ull;
15 typedef pair<int,int> PII;
16 typedef vector<int> VI;
17 #define fi first
18 #define se second
19 #define MP make_pair
20 #define N   1100000
21 #define MOD 1000000007
22 #define eps 1e-8
23 #define pi  acos(-1)
24 
25 
26 int n;
27 double L;
28 
29 
30 int read()
31 {
32    int v=0,f=1;
33    char c=getchar();
34    while(c<48||57<c) {if(c=='-') f=-1; c=getchar();}
35    while(48<=c&&c<=57) v=(v<<3)+v+v+c-48,c=getchar();
36    return v*f;
37 }
38 
39 int main()
40 {
41     while(scanf("%d%lf",&n,&L)!=EOF)
42     {
43          double ans=0;
44          for(int i = 1; i <= n; ++i)
45          {
46              double x;
47              scanf("%lf",&x);
48              x/=180*1.0;
49              x*=pi*1.0;
50              ans+=1.0/2*L*L*sin(x);
51          }
52          printf("%.3lf
",ans);
53     }
54     return 0;
55 }