一个字[绝]

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
#define MAXN 1000000+10
int n,l,r;
int a,b,c;
int  x[MAXN];
long long sum[MAXN],f[MAXN];
int q[MAXN];
long long sqr(long long  x){return x*x;}
inline double slop(int k,int j){return (double)(f[j]-f[k]+a*(sqr(sum[j])-sqr(sum[k]))+b*(sum[k]-sum[j]))/(double)(2*a*(sum[j]-sum[k]));}
int main()
{
    scanf("%d%d%d%d",&n,&a,&b,&c);
    for(int i=1;i<=n;i++)scanf("%d",&x[i]);
    for(int i=1;i<=n;i++)sum[i]=sum[i-1]+x[i];
    for(int i=1;i<=n;i++){
        while(l<r&&slop(q[l],q[l+1])<sum[i])l++;
        int t=q[l];
        f[i]=f[t]+a*sqr(sum[i]-sum[t])+b*(sum[i]-sum[t])+c;
        while(l<r&&slop(q[r-1],q[r])>slop(q[r],i))r--;
        q[++r]=i;
    }
    printf("%lld",f[n]);
    return 0;
}