bzoj 1911 [Apio2010]特别行动队（斜率优化+DP）

 1 #include<cstdio>
 2 #include<iostream>
 3 using namespace std;
 4 
 5 typedef long long LL;
 6 const int N = 1000000+10;
 7 struct point { LL x,y;
 8 }q[N],now;
 9 int n,a,b,c,L,R;  LL C[N];
10 
11 LL cross(point a,point b,point c) {
12     return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
13 }
14 void read(LL& x) {
15     char c=getchar(); while(!isdigit(c)) c=getchar();
16     x=0; while(isdigit(c)) x=x*10+c-‘0‘ , c=getchar();
17 }
18 int main() {
19     scanf("%d%d%d%d",&n,&a,&b,&c);
20     for(int i=1;i<=n;i++)
21         read(C[i]) , C[i]+=C[i-1];
22     for(int i=1;i<=n;i++) {
23         while(L<R && q[L].y-2*a*C[i]*q[L].x <= q[L+1].y-2*a*C[i]*q[L+1].x) L++;
24         now.x=C[i];
25         now.y=q[L].y-2*a*C[i]*q[L].x+2*a*C[i]*C[i]+c;
26         while(L<R && cross(q[R-1],now,q[R])<=0) R--;
27         q[++R]=now;
28     }
29     printf("%lld",q[R].y+b*C[n]-a*C[n]*C[n]);
30     return 0;
31 }