bzoj1492 [NOI2007]货币兑换Cash

传送门：[Submit]

本来写了一个详细的题解。。。。。。。。

但是TM博客园不保存。。。。。。

于是我就直接复制论文了吧。。。。

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cstring>
#include<cmath>
#define eps 1e-9
#define inf 0x7fffffff
#define ll long long
#define N 100005
using namespace std;
struct data{double a,b,rate,k,x,y; int id;
}q[N],t[N];
double f[N];
int s[N];
int n;
bool cmp(data a, data b){ return a.k>b.k;
}
double getk(int a,int b)
{
    if(!b)return -1e20;
    if(fabs(q[a].x-q[b].x)<eps)return 1e20;
    return (q[b].y-q[a].y)/(q[b].x-q[a].x);
}
void solve(int l,int r)
{
    if (l==r)
    {
        f[l]=max(f[l],f[l-1]);
        q[l].y=f[l]/(q[l].b+q[l].rate*q[l].a);
        q[l].x=q[l].rate*q[l].y;
        return;
    }
    int mid=(l+r)>>1,l1=l,l2=mid+1;
    for (int i=l; i<=r; i++)
        if (q[i].id<=mid) t[l1++]=q[i]; else t[l2++]=q[i];
    for (int i=l; i<=r; i++) q[i]=t[i];
    solve(l,mid);
    int top=0;
    for (int i=l; i<=mid; i++)
    {
        while (top>1 && getk(s[top-1],s[top]) < getk(s[top-1],i)+eps)top--;
        s[++top]=i;
    }
    s[++top]=0;
    int j=1;
    for (int i=mid+1; i<=r; i++)
    {
        while (j<top && getk(s[j],s[j+1])+eps > q[i].k) j++;
        f[q[i].id]=max(f[q[i].id],q[s[j]].x*q[i].a+q[s[j]].y*q[i].b);
    }
    solve(mid+1,r);
    l1=l;l2=mid+1;
    for (int i=l; i<=r; i++) 
        if ((q[l1].x<q[l2].x || l2>r) && l1<=mid) t[i]=q[l1++]; else t[i]=q[l2++];
    for (int i=l; i<=r; i++) q[i]=t[i];
}
int main()
{
    scanf("%d%lf",&n,&f[0]);
    for (int i=1; i<=n; i++)
    {
        scanf("%lf%lf%lf",&q[i].a,&q[i].b,&q[i].rate);
        q[i].k=-q[i].a/q[i].b; q[i].id=i;
    }
    sort(q+1,q+1+n,cmp);
    solve(1,n);
    printf("%0.3lf",f[n]);
}

日常一膜：CYS,CYY,LS,YZW,YWF,OYZX..............