NOI2012 骑行川藏

http://www.lydsy.com/JudgeOnline/problem.php?id=2876

表示完全不会。。。。。。

还是跪拜大神吧

http://www.cnblogs.com/GerynOhenz/p/4698451.html

#include<cstdio>
#include<cstdlib>
#include<iostream>
#include<fstream>
#include<algorithm>
#include<cstring>
#include<string>
#include<cmath>
#include<queue>
#include<stack>
#include<map>
#include<utility>
#include<set>
#include<bitset>
#include<vector>
#include<functional>
#include<deque>
#include<cctype>
#include<climits>
#include<complex>
//#include<bits/stdc++.h>适用于CF,UOJ，但不适用于poj

using namespace std;

typedef long long LL;
typedef double DB;
typedef pair<int,int> PII;
typedef complex<DB> CP;

#define mmst(a,v) memset(a,v,sizeof(a))
#define mmcy(a,b) memcpy(a,b,sizeof(a))
#define fill(a,l,r,v) fill(a+l,a+r+1,v)
#define re(i,a,b)  for(i=(a);i<=(b);i++)
#define red(i,a,b) for(i=(a);i>=(b);i--)
#define ire(i,x) for(typedef(x.begin()) i=x.begin();i!=x.end();i++)
#define fi first
#define se second
#define m_p(a,b) make_pair(a,b)
#define SF scanf
#define PF printf
#define two(k) (1<<(k))

template<class T>inline T sqr(T x){return x*x;}
template<class T>inline void upmin(T &t,T tmp){if(t>tmp)t=tmp;}
template<class T>inline void upmax(T &t,T tmp){if(t<tmp)t=tmp;}

const DB EPS=1e-10;
inline int sgn(DB x){if(abs(x)<EPS)return 0;return(x>0)?1:-1;}
const DB Pi=acos(-1.0);

inline int gint()
  {
        int res=0;bool neg=0;char z;
        for(z=getchar();z!=EOF && z!=‘-‘ && !isdigit(z);z=getchar());
        if(z==EOF)return 0;
        if(z==‘-‘){neg=1;z=getchar();}
        for(;z!=EOF && isdigit(z);res=res*10+z-‘0‘,z=getchar());
        return (neg)?-res:res;
    }
inline LL gll()
  {
      LL res=0;bool neg=0;char z;
        for(z=getchar();z!=EOF && z!=‘-‘ && !isdigit(z);z=getchar());
        if(z==EOF)return 0;
        if(z==‘-‘){neg=1;z=getchar();}
        for(;z!=EOF && isdigit(z);res=res*10+z-‘0‘,z=getchar());
        return (neg)?-res:res;
    }

const int maxN=10000;

int N;
DB E,s[maxN+10],k[maxN+10],tv[maxN+10],v[maxN+10];
DB lambda,ans;

inline void calc_v()
  {
      int i;
      re(i,1,N)
        {
            DB L=0.0,R=1e4;
            while(L<R)
              {
                  DB mid=(L+R)/2.0,temp=2.0*k[i]*sqr(mid)*(mid-tv[i]);
                  if(sgn(temp-lambda)==0)
                    {
                        v[i]=mid;
                        break;
                    }
                  if(temp<lambda) L=mid; else R=mid;
              }
        }
  }

inline int check()
  {
      int i;
      DB res=0.0;
      re(i,1,N)res+=k[i]*sqr(v[i]-tv[i])*s[i];
      return res<=E;
  }

inline void calc_ans(){int i;ans=0.0;re(i,1,N)ans+=s[i]/v[i];}

inline void solve()
  {
      DB L=0.0,R=1e5;
      while(L+EPS<R)
        {
            lambda=(L+R)/2.0;
            calc_v();
            if(check()) L=lambda; else R=lambda;
        }
      calc_v();
      calc_ans();
  }

int main()
  {
      /*freopen("bicycling.in","r",stdin);
      freopen("bicycling.out","w",stdout);*/
        int i;
        SF("%d %lf\n",&N,&E);
        re(i,1,N)SF("%lf %lf %lf\n",&s[i],&k[i],&tv[i]);
        solve();
        PF("%0.8lf\n",ans);
        return 0;
    }