【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\n",ans); 53 } 54 return 0; 55 }
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