SGU 417. Heavy Disc（水题）

红太狼 2022-06-05 05:58 134阅读 0赞

#### 417. Heavy Disc ####

Time limit per test: 0.5 second(s)  
Memory limit: 262144 kilobytes

input: standard  
output: standard

Consider a heavy disc on the plane, centered at ( *x* 0, *y* 0) with radius *r*, with the origin strictly outside it. The density of the disc is given by formula  
  
![3ffbc090b4ecfa52dcb694fb8fa7eab7_v_1511072356][]  
  
What is the mass of the disc?

**Input**

The input file contains three integer numbers *x* 0, *y* 0, *r* (-100 ≤ *x* 0, *y* 0 ≤ 100, 1 ≤ *r* ≤ 100, *x* 0 2\+ *y* 0 22).

**Output**

Output one real number — the mass of the disc. Your answer will be considered correct if it is within 10 \-12 relative error of the exact answer.

**Example(s)**

<table style="border-collapse:collapse; border:1px solid black"> 
 <tbody> 
  <tr> 
   <td style="border-collapse:collapse; border:1px solid black"> <pre style="white-space:pre-wrap; word-wrap:break-word">sample input</pre> </td> 
   <td style="border-collapse:collapse; border:1px solid black"> <pre style="white-space:pre-wrap; word-wrap:break-word">sample output</pre> </td> 
  </tr> 
  <tr> 
   <td style="border-collapse:collapse; border:1px solid black"> <pre style="white-space:pre-wrap; word-wrap:break-word">3 4 2
</pre> </td> 
   <td style="border-collapse:collapse; border:1px solid black"> <pre style="white-space:pre-wrap; word-wrap:break-word">40.449586576894895
</pre> </td> 
  </tr> 
 </tbody> 
</table>

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<table> 
 <tbody> 
  <tr style="background-color:rgb(255,255,255)"> 
   <td align="right"><a href="mailto:acm@cs.sgu.ru" rel="nofollow">Online Contester</a>&nbsp;Team © 2002 - 2010. All rights reserved.</td> 
  </tr> 
 </tbody> 
</table>

Input

The input file contains three integer numbers *x* 0, *y* 0, *r* (-100 ≤ *x* 0, *y* 0 ≤ 100, 1 ≤ *r* ≤ 100, *x* 0 2\+ *y* 0 22).

Output

Output one real number — the mass of the disc. Your answer will be considered correct if it is within 10 \-12 relative error of the exact answer.

Sample Input

题解：

乍一看以为要积分求公式。。求了半天后来发现根本没法求，这题很迷，总感觉题目有歧义，只要用圆心密度乘圆面积就能a，excuse me！！？？做出来的应该都是没法求凑到的答案，因为这题真的很垃圾，感觉没有任何意义

代码：

#include<stdio.h>
    #include<string.h>
    #include<stdlib.h>
    #include<queue>
    #include<stack>
    #include<math.h>
    #include<vector>
    #include<map>
    #include<set>
    #include<stdlib.h>
    #include<cmath>
    #include<string>
    #include<algorithm>
    #include<iostream>
    using namespace std;
    #define lson k*2
    #define rson k*2+1
    #define M (t[k].l+t[k].r)/2
    #define ll long long
    #define INF 10086111
    const double pi=acos(0)*2;
    int main()
    {
    	double x,y,r,r1,r2;
    	while(scanf("%lf%lf%lf",&x,&y,&r)!=EOF)
        {
            printf("%.12lf\n",pi*r*r*log(x*x+y*y));
        }
        return 0;
    }

[3ffbc090b4ecfa52dcb694fb8fa7eab7_v_1511072356]: https://odzkskevi.qnssl.com/3ffbc090b4ecfa52dcb694fb8fa7eab7?v=1511072356