C++(clang++ 11.0.1) 解法, 执行用时: 122ms, 内存消耗: 6432K, 提交时间: 2022-09-07 14:11:43

#include<bits/stdc++.h>
#define ls (p<<1)
#define rs (p<<1|1)
#define mid ((l+r)>>1)
using namespace std;
const int N=1e5+7;

int n,u,tr[N<<2];
double F,G,c[N];

struct Nod{
	double a,b,c,k,x,y;
}s[N];

inline double fc(int i,int t){
	return (s[t].y+s[t].x*c[i]);
}

void update(int p,int t,int l,int r){
	if(l==r){
		if(fc(l,t)>fc(l,tr[p])) tr[p]=t;
		return;
	}
	if(fc(mid,t)>fc(mid,tr[p])) swap(t,tr[p]);
	if(fc(l,t)>fc(l,tr[p])) update(ls,t,l,mid);
	else update(rs,t,mid+1,r);
}

inline double query(int p,int l,int r){
	if(l==r) return fc(u,tr[p]);
	return max(fc(u,tr[p]),(u>mid)?query(rs,mid+1,r):query(ls,l,mid));
}

signed main(){
	scanf("%d%lf",&n,&F);
	for(int i=1;i<=n;++i){
		scanf("%lf%lf%lf",&s[i].a,&s[i].b,&s[i].k);
		s[i].c=s[i].a/s[i].b;
		c[i]=s[i].c;
	}
	stable_sort(c+1,c+1+n);
	for(int i=1;i<=n;++i){
		u=lower_bound(c+1,c+1+n,s[i].c)-c;
		F=max(F,s[i].b*query(1,1,n));
		G=s[i].a*s[i].k+s[i].b;
		s[i].x=F*s[i].k/G;
		s[i].y=F/G;
		update(1,i,1,n);
	//	cout<<u<<" "<<F<<" "<<G<<" "<<s[i].x<<" "<<s[i].y<<"\n";
	}
	printf("%.3lf",F);
	return 0;
}