[bzoj1911][Apio2010]特别行动队

#include<set> 
#include<cmath>
#include<ctime>
#include<queue>
#include<stack>
#include<cstdio>
#include<vector>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define N 1000001
using namespace std;
typedef long long ll;
ll f[N],s[N],q[N],a,b,c,n,h,t;
inline ll sqr(ll k){
    return k*k;
}
inline ll y(ll k){
    return a*sqr(s[k])+b*s[k]+c;
}
inline ll g(ll k){
    return f[k]+a*sqr(s[k])-b*s[k];
}
inline ll func(ll k){
    return a*sqr(k)+b*k+c;
} 
inline double cmp(ll p,ll q){
    return (double)(g(q)-g(p))/(double)(s[q]-s[p]);
}
inline void init(){
    scanf("%lld%lld%lld%lld",&n,&a,&b,&c);
    for(ll i=1;i<=n;i++){
        scanf("%lld",&s[i]);
        s[i]+=s[i-1];
    }
    for(ll i=1,k;i<=n;i++){
        k=(a<<1)*s[i];
        while(h<t&&cmp(q[h],q[h+1])>k) h++;
        f[i]=f[q[h]]+func(s[i]-s[q[h]]);
        while(h<t&&cmp(q[t],i)>cmp(q[t-1],q[t]))
            t--;
        q[++t]=i;
    }
    printf("%lld\n",f[n]);
}
int main(){
    freopen("commando.in","r",stdin);
    freopen("commando.out","w",stdout);
    init();
    fclose(stdin);
    fclose(stdout);
    return 0;
}