LOJ P10016 灯泡 题解

每日一题 day50 打卡

Analysis

用初中学的相似推一波式子，再用三分一搞就好了。

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define int long long
 #define rep(i,s,e) for(register int i=s;i<=e;++i)
 #define dwn(i,s,e) for(register int i=s;i>=e;--i)
 using namespace std;
 inline int read()
 {
     int x=,f=;
     char c=getchar();
     while(c<''||c>'') {if(c=='-') f=-; c=getchar();}
     while(c>=''&&c<='') {x=x*+c-''; c=getchar();}
     return f*x;
 }
 inline void write(int x)
 {
     if(x<) {putchar('-'); x=-x;}
     if(x>) write(x/);
     write(x%+'');
 }
 int T;
 double H,h,D;
 double L1,L2;
 double calc(double x)
 {
     double dis=(double)(H*x)/(double)(H-h);
 //    cout<<"dis:"<<dis<<" "<<"fz:"<<(double)(H*x)<<" "<<"fm:"<<(double)(H-h)<<" x:"<<x<<endl;
     if(dis<=D) return dis-x;
     else
     {
         L1=(double)(D-x);
         L2=((double)(D*h)-(double)(L1*H))/(double)(D-L1);
         return L1+L2;
     }
 }
 signed main()
 {
     T=read();
     while(T--)
     {
         scanf("%lf%lf%lf",&H,&h,&D);
         double l=0.0,r=D;
         while(r-l>=1e-)
         {
             double mid1=l+(r-l)/,mid2=r-(r-l)/;
 //            cout<<"l:"<<l<<" "<<"r:"<<r<<" "<<"mid1:"<<mid1<<" "<<"mid2:"<<mid2<<endl;
             if(calc(mid1)<=calc(mid2)) l=mid1;
             else r=mid2;
 //            system("pause");
         }
         printf("%.3lf\n",calc(l));
     }
     return ;
 }

请各位大佬斧正（反正我不认识斧正是什么意思）