2018 Multi-University Training Contest 6 Solution

A - oval-and-rectangle

题意：给出一个椭圆的a 和 b，在$[0, b]中随机选择c$ 使得四个顶点在椭圆上构成一个矩形，求矩形周长期望

思路：求出每种矩形的周长，除以b（积分）

 1 #include<bits/stdc++.h>
 2 
 3 using namespace std;
 4 
 5 const double PI = acos(-1.0);
 6 
 7 double a, b;
 8 
 9 void RUN()
10 {
11     int t;
12     scanf("%d", &t);
13     while (t--)
14     {
15         scanf("%lf %lf", &a, &b);
16         double ans = 2 * b + a * PI;
17         printf("%.6f\n", ans - 5e-7);
18     }
19 }
20 
21 int main()
22 {
23 #ifdef LOCAL_JUDGE
24     freopen("Text.txt", "r", stdin);
25 #endif // LOCAL_JUDGE
26 
27     RUN();
28 
29 #ifdef LOCAL_JUDGE
30     fclose(stdin);
31 #endif // LOCAL_JUDGE
32     return 0;
33 }

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