[Apio2010]特别行动队

1911: [Apio2010]特别行动队

Description

Input

Output

Sample Input

Sample Output

HINT

#include<cstdio>
#include<iostream>
#include<algorithm>
#define N 1000001
using namespace std;
int q
,head,tail;
long long dp
,sum
,a,b,c,n;
void read(long long &x)
{
x=0; int f=1; char c=getchar();
while(!isdigit(c)) { if(c=='-') f=-1; c=getchar();}
while(isdigit(c)) { x=x*10+c-'0'; c=getchar(); }
x*=f;
}
long long up(int k,int j)
{
return dp[j]-dp[k]+a*(sum[j]*sum[j]-sum[k]*sum[k])+b*(sum[k]-sum[j]);
}
long long down(int k,int j)
{
return 2*(sum[j]-sum[k]);
}
int main()
{
read(n);
read(a); read(b); read(c);
for(int i=1;i<=n;i++)
{
read(sum[i]);
sum[i]+=sum[i-1];
}
int j;
for(int i=1;i<=n;i++)
{
while(head<tail && up(q[head],q[head+1])>=down(q[head],q[head+1])*sum[i]*a) head++;
j=q[head];
dp[i]=dp[j]+a*(sum[i]-sum[j])*(sum[i]-sum[j])+b*(sum[i]-sum[j])+c;
while(head<tail && up(q[tail-1],q[tail])*down(q[tail],i)<=up(q[tail],i)*down(q[tail-1],q[tail])) tail--;
q[++tail]=i;
}
printf("%lld",dp
);
}