bzoj1492 [NOI2007]货币兑换Cash

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<algorithm>
 5 #include<cstring>
 6 #include<cmath>
 7 #define eps 1e-9
 8 #define inf 0x7fffffff
 9 #define ll long long
10 #define N 100005
11 using namespace std;
12 struct data{double a,b,rate,k,x,y; int id;
13 }q[N],t[N];
14 double f[N];
15 int s[N];
16 int n;
17 bool cmp(data a, data b){ return a.k>b.k;
18 }
19 double getk(int a,int b)
20 {
21     if(!b)return -1e20;
22     if(fabs(q[a].x-q[b].x)<eps)return 1e20;
23     return (q[b].y-q[a].y)/(q[b].x-q[a].x);
24 }
25 void solve(int l,int r)
26 {
27     if (l==r)
28     {
29         f[l]=max(f[l],f[l-1]);
30         q[l].y=f[l]/(q[l].b+q[l].rate*q[l].a);
31         q[l].x=q[l].rate*q[l].y;
32         return;
33     }
34     int mid=(l+r)>>1,l1=l,l2=mid+1;
35     for (int i=l; i<=r; i++)
36         if (q[i].id<=mid) t[l1++]=q[i]; else t[l2++]=q[i];
37     for (int i=l; i<=r; i++) q[i]=t[i];
38     solve(l,mid);
39     int top=0;
40     for (int i=l; i<=mid; i++)
41     {
42         while (top>1 && getk(s[top-1],s[top]) < getk(s[top-1],i)+eps)top--;
43         s[++top]=i;
44     }
45     s[++top]=0;
46     int j=1;
47     for (int i=mid+1; i<=r; i++)
48     {
49         while (j<top && getk(s[j],s[j+1])+eps > q[i].k) j++;
50         f[q[i].id]=max(f[q[i].id],q[s[j]].x*q[i].a+q[s[j]].y*q[i].b);
51     }
52     solve(mid+1,r);
53     l1=l;l2=mid+1;
54     for (int i=l; i<=r; i++) 
55         if ((q[l1].x<q[l2].x || l2>r) && l1<=mid) t[i]=q[l1++]; else t[i]=q[l2++];
56     for (int i=l; i<=r; i++) q[i]=t[i];
57 }
58 int main()
59 {
60     scanf("%d%lf",&n,&f[0]);
61     for (int i=1; i<=n; i++)
62     {
63         scanf("%lf%lf%lf",&q[i].a,&q[i].b,&q[i].rate);
64         q[i].k=-q[i].a/q[i].b; q[i].id=i;
65     }
66     sort(q+1,q+1+n,cmp);
67     solve(1,n);
68     printf("%0.3lf",f[n]);
69 }