bzoj1911 [Apio2010]特别行动队commando

题目链接

斜率优化

 #include<cstdio>
 #include<cstdlib>
 #include<string>
 #include<cstring>
 #include<cmath>
 #define re(i,l,r) for(int i=(l);i<=(r);i++)
 using namespace std;
 typedef long long LL;
 template<typename Q>
 void inin(Q &x)
 {
     x=;int f=;char ch=getchar();
     while(ch<''||ch>''){if(ch=='-')f=;ch=getchar();}
     while(ch>=''&&ch<='')x=(x<<)+(x<<)+ch-'',ch=getchar();
     x=f?-x:x;
 }
 int n,a,b,c;
 LL sum[],x[],y[],aa[],dp[];
 int q[];
 LL f(const LL &a){return a*a;}
 int main()
 {
     inin(n);inin(a),inin(b),inin(c);
     re(i,,n)inin(aa[i]),sum[i]=sum[i-]+aa[i];
     re(i,,n)x[i]=1LL*a*sum[i];
     int l=,r=;
     re(i,,n)
     {
         while(l<r&&y[q[l+]]-y[q[l]]>2LL*sum[i]*(x[q[l+]]-x[q[l]]))l++;
         int t=q[l];
         dp[i]=dp[t]+1LL*f(sum[i]-sum[t])*a+1LL*(sum[i]-sum[t])*b+c;
         y[i]=dp[i]+1LL*a*f(sum[i])-1LL*b*sum[i];
         while(l<r&&(y[q[r]]-y[q[r-]])*(x[i]-x[q[r]])>(y[i]-y[q[r]])*(x[q[r]]-x[q[r-]]))r--;
         q[++r]=i;
     }
     printf("%lld",dp[n]);
     return ;
 }