ZOJ 3203 Light Bulb

在LJOJ上说这是三分，我就懒得去推公式了。学习三分法第一题。十分方便。

//By Richard
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <ctime>
#define rep(x,y,z) for (int x=(y);(x)<=(z);(x)++)
#define per(x,y,z) for (int x=(y);(x)>=(z);(x)--)
#define log2(x) (31-__builtin_clz(x))
#define mod (int)(1e9+7)
#define inf 0x3f3f3f3f
#define cls(x) memset(x,0,sizeof(x))
#ifdef DEBUG
#define debugdo(X) X
#define debugndo(X)
#define debugout(X) cout<<(#X)<<"="<<(X)<<endl
#else
#define debugdo(X)
#define debugndo(X) X
#define debugout(X)
#endif // debug
#ifdef ONLINE_JUDGE
#define debugdo(X)
#define debugndo(X)
#define debugout(X)
#endif
#define putarray(x,n) rep(iiii,1,n) printf("%d ",x[iiii])
#define mp make_pair
using namespace std;
typedef pair<int,int> pairs;
typedef long long LL;
/////////////////////read3.0////////////////////////////////////
template <typename T>
inline void read(T &x){char ch;x=0;bool flag=false;ch=getchar();while (ch>'9'||ch<'0') {ch=getchar();if (ch=='-') flag=true;}while ((ch<='9'&&ch>='0')){x=x*10+ch-'0';ch=getchar();}if (flag) x*=-1;}
template <typename T>
inline void read(T &x,T &y){read(x);read(y);}
/////////////////variables&functions////////////////////


int T;
double H,h,D;
const double eps=0.0000001;
// #define calc(x) (x+((h/(x+(hD-Hx)/(H-h)))(hD-Hx)/(H-h)))
// #define calc(x) (x+((hD-Hx)/(D-x)))
inline double calc(double x)
{
    double temp=(hD-H*x)/(D-x);
    if (temp>0) return x+temp;
    else return (D-x)/(H-h);
}
int main()
{
    read(T);
    while (T–)
    {
        scanf("%lf%lf%lf",&H,&h,&D);
        double l=0,r=D;
        while (r-l>eps)
        {
            double ll=(r-l)/3+l,rr=(r-l)*2/3+l;
            double ansll=calc(ll),ansrr=calc(rr);
            if (ansll>ansrr) r=rr;
            else l=ll;
        }
        printf("%.3lf\n",calc(l));
    }
    return 0;
}