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=0,f=1;
    char c=getchar();
    while(c<'0'||c>'9') {if(c=='-') f=-1; c=getchar();}
    while(c>='0'&&c<='9') {x=x*10+c-'0'; c=getchar();}
    return f*x;
}
inline void write(int x)
{
    if(x<0) {putchar('-'); x=-x;}
    if(x>9) write(x/10);
    write(x%10+'0');
}
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-11)
        {
            double mid1=l+(r-l)/3,mid2=r-(r-l)/3;
//            cout<<"l:"<<l<<" "<<"r:"<<r<<" "<<"mid1:"<<mid1<<" "<<"mid2:"<<mid2<<endl;
            if(calc(mid1)<=calc(mid2)) l=mid1;
            else r=mid2;
//            system("pause");
        }
        printf("%.3lf
",calc(l));
    }
    return 0;
}

请各位大佬斧正（反正我不认识斧正是什么意思）