hdu 3507 Print Article

#include<cstdio>
#include<cstring>
#define N 500001
using namespace std;
typedef long long LL;
LL sum[N],dp[N];
int c,q[N],head,tail; 
long long up(int k,int j) 
{
    return dp[j]-dp[k]-sum[k]*sum[k]+sum[j]*sum[j];
}
long long down(int k,int j)
{
    return 2*(sum[j]-sum[k]);
}
int main()
{
    int n,m,x;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        memset(sum,0,sizeof(sum));
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&x);
            sum[i]=sum[i-1]+x;
        }
        head=tail=0;
        memset(q,0,sizeof(q));
        memset(dp,0,sizeof(dp));
        for(int i=1;i<=n;i++)
        {
            while(head<tail && up(q[head],q[head+1])<=sum[i]*down(q[head],q[head+1])) head++;
            dp[i]=dp[q[head]]+m+(sum[i]-sum[q[head]])*(sum[i]-sum[q[head]]);
            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\n",dp[n]);
    }
}