bzoj 1911: [Apio2010]特别行动队

呃呃呃，和平方的有什么区别吗。。

#include <bits/stdc++.h>
#define LL long long
#define lowbit(x) x&(-x)
#define inf 0x3f3f3f3f
#define eps 1e-5
#define N 1000005
using namespace std;
inline int ra()
{
    int x=0,f=1; char ch=getchar();
    while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();}
    while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
LL sum[N],f[N];
int A,B,C,n,q[N];
double slope(int j, int k)
{
    return (double)((f[j]+A*sum[j]*sum[j]-B*sum[j])-(f[k]+A*sum[k]*sum[k]-B*sum[k]))/(double)(2*A*(sum[j]-sum[k]));
}
int main(int argc, char const *argv[])
{
    n=ra(); A=ra(); B=ra(); C=ra();
    for (int i=1; i<=n; i++) sum[i]=sum[i-1]+ra();
    int l=0,r=0;
    for (int i=1; i<=n; i++)
    {
        while (l<r && slope(q[l+1],q[l])<=(double)sum[i]) l++;
        int t=q[l];
        f[i]=f[t]+A*(sum[i]-sum[t])*(sum[i]-sum[t])+B*(sum[i]-sum[t])+C;
        while (l<r && slope(q[r],q[r-1])>=slope(i,q[r])) r--;
        q[++r]=i;
    }
    cout<<f[n];
    return 0;
}