2 solutions

  • 3
    @ 2022-12-18 20:47:44

    这道题花了我一个多小时,最后发现PI写错了

    ①PI=acos(-1)而我写成了PI=cos(-1),一度怀疑人生

    ②r1的求解比较难想到,是利用的三角函数 看图吧! image

    //非(常规)二分,含有精度,估算高度而不是去计算高度
    //使用到eps的l,r不需要+1-1
    #include<iostream>
    #include<math.h>
    using namespace std;
    #define PI acos(-1)
    double r, R, H, V, v2, r1;
    bool check(double h) {
    	r1 = (h / H) * (R - r) + r;
    	v2 = (1.0 / 3.0) * PI * h * (r1 * r1 + r * r1 + r * r);
    	return v2 <= V;
    }
    int main() {
    	int t;
    	scanf("%d", &t);
    	while (t--) {
    		scanf("%lf%lf%lf%lf", &r, &R, &H, &V);
    		double l = 0, r = 100, mid;
    		while (r - l > 1e-7) {
    			mid = (l + r) / 2;
    			if (check(mid)) l=mid;
    			else r=mid;
    		}
    		printf("%.6lf", r);
    	}
    	return 0;
    }
    
    • 0
      @ 2022-2-12 17:25:59

      二分,条件找好,取号精度就可以了

      #include<iostream>
      using namespace std;
      #define pai 3.141592653589
      
      int t;
      double rd,ru,h,v;
      
      bool check(double H,double r){
      	double V=(1.0/3.0)*pai*H*(rd*rd+r*r+r*rd);
      	if(V<=v)return false;
      	else return true;
      }
      
      double find(double l,double r){
      	double mid,R;
      	while(l<=r){
      		mid=(r+l)/2.0;
      		R=mid*(ru-rd)/h+rd;
      		if(check(mid,R))r=mid-0.0000001;
      		else l=mid+0.0000001;
      	}
      	return l;
      }
      
      int main(){
      	cin>>t;
      	while(t--){
      		cin>>rd>>ru>>h>>v;
      		double ans=find(0,h);
      		printf("%.6lf",ans);
      	}
      	return 0;
      }
      
      • 1

      Information

      ID
      282
      Time
      1000ms
      Memory
      256MiB
      Difficulty
      6
      Tags
      # Submissions
      116
      Accepted
      35
      Uploaded By