bzoj1492 斜率优化|cdq分治

 #include <stdio.h>
 #include <bitset>
 #include <string.h>
 #include <stack>
 #include <algorithm>
 #include <iostream>
 #include <set>
 #include <map>
 #include <math.h>
 #include <queue>
 #include <complex>
 using namespace std ;
 typedef long long ll ;
 typedef long double ld ;
 typedef unsigned long long ull ;
 #ifdef _WIN32
 #define LLD "%I64d"
 #else
 #define LLD "%lld"
 #endif
 #define pi (acos(-1.0))
 #define fi first
 #define se second
 #define lson (o<<1),l,mid
 #define rson (o<<1|1),mid+1,r
 #define MP make_pair
 #define sqr(x) ((x)*(x))
 #define ALL(v) (v).begin(),(v).end()
 #define showtime fprintf(stderr,"time = %.15f\n",clock() / (double)CLOCKS_PER_SEC)
 const double eps = 1e-;
 const int inf = 0x3f3f3f3f ;
 const ll INF = (ll)4e18 ;
 const int MOD=(int)1e9+,BAS=,invBAS=;
 int sign(double x){return x<-eps?-:x>eps;}

 const int M =  ;
 struct Point {
     int id ;
     double a,b,rate,x,y ;
     inline void minus (Point t) {
         x-=t.x ; y-=t.y ;
     }
     inline double mul (Point t) {
         return x*t.y-y*t.x ;
     }
     inline bool operator < (const Point &t) {
         if (sign(x-t.x)==) return y>t.y ;
         return x<t.x ;
     }
 } p[M] , c[M] ;
 int n , st[M] , sz ;
 double money[M] ;

 double slope (Point e,Point t,Point g) {
     e.minus(g) ; t.minus(g) ;
     return sign(t.mul(e))<= ;
 }

 double get (int i,int j) {
     return p[i].x*p[j].b+p[i].y*p[j].a ;
 }

 void cdq (int l,int r) {
     if (l == r) {
         money[l] = max(money[l-],money[l]) ;
         p[l].x = money[l]/(p[l].a*p[l].rate+p[l].b) ;
         p[l].y = p[l].x*p[l].rate ;
         return ;
     }
     int mid = l+r>> ;
     for (int i=l,j=,k=; i<=r ; i ++)
         if (p[i].id<=mid) c[l+j++] = p[i] ;
         else c[mid+k++] = p[i] ;
     memcpy (p+l,c+l,sizeof(Point)*(r-l+)) ;
     cdq (l,mid) ;
     sz =  ;
     for (int i=l ; i<=mid ; i++) {
         if (sz && sign(p[st[sz-]].x-p[i].x)==) continue ;
         while (sz>&&slope(p[st[sz-]],p[st[sz-]],p[i]))sz --;
         st[sz++] = i ;
     }
     for (int i=mid+ ; i<=r ; i++) {
         while (sz> && sign(get(st[sz-],i)-get(st[sz-],i))>) sz -- ;
         money[p[i].id] = max (money[p[i].id] , get(st[sz-],i)) ;
     }
     cdq (mid+,r) ;
     int e=l , t=mid+ ;
     for (int i=l ; i<=r ; i++)
         if (e<=mid && (t>r || p[e]<p[t])) c[i] = p[e++] ;
         else c[i] = p[t++] ;
     memcpy(p+l,c+l,sizeof(Point)*(r-l+)) ;
 }

 bool cmp (const Point &e , const Point &t) { return e.b*t.a>t.b*e.a ; }

 int main () {
     scanf ("%d%lf" , &n , money) ;
     for (int i= ; i<n ; i ++) {
         scanf ("%lf%lf%lf" , &p[i].a,&p[i].b,&p[i].rate);
         p[i].id = i ;
     }
     sort (p,p+n,cmp) ;
     cdq (,n-) ;
     printf ("%.3f\n" , money[n-]) ;
     return  ;
 }